Zinc ion battery and preparation method thereof

Abstract

The invention discloses a zinc ion battery and a preparation method thereof, the zinc ion battery comprises a positive electrode, a negative electrode, a diaphragm and an electrolyte, and the zinc ion battery is characterized in that the positive electrode comprises a vanadium-based material, and the vanadium-based material comprises vanadium pentoxide intercalated by water molecules and metal ions and an MXene coating layer; the electrolyte comprises zinc salt, water and an additive, the additive comprises positive ions and negative ions, and the negative ions have the structure shown in the formula I. According to the zinc ion battery, water molecules and metal ions are used for intercalating vanadium pentoxide and coating MXene, and the water molecules and the metal ions are cooperatively used with the electrolyte with specific composition, so that ions can be quickly intercalated / deintercalated, the intrinsic conductivity of the material is enhanced, the structure of the material is stabilized, vanadium dissolution / metal ion dissolution at the positive electrode side can be prevented, and the service life of the zinc ion battery is prolonged. And the side reactions of interface hydrogen evolution and corrosion caused by decomposition of active water molecules on the zinc negative electrode side are synergistically inhibited. Through the comprehensive action of the factors, the zinc ion battery has excellent electrochemical performance.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to a zinc-ion battery and its preparation method. Background Technology

[0002] Zinc-ion batteries, as an emerging electrochemical energy storage device, possess multiple advantages. First, zinc resources are abundant, inexpensive, environmentally friendly, and non-toxic. Second, zinc-ion batteries typically use aqueous electrolytes, fundamentally eliminating the safety hazards of flammable and explosive organic electrolytes, resulting in extremely high safety. In terms of electrochemical performance, zinc undergoes a double-electron transfer reaction, leading to a theoretically high volumetric energy density. Furthermore, the zinc anode fabrication process is relatively simple, and the battery structure is easy to integrate, making it suitable for large-scale energy storage applications. Overall, zinc-ion batteries demonstrate significant potential in terms of safety, cost, and resource sustainability, serving as an important complement to existing lithium-ion battery technologies.

[0003] Among numerous cathode materials, vanadium-based materials (such as vanadium oxides and their derivatives) are considered highly promising candidates due to their unique physicochemical properties. Vanadium oxides typically possess layered, tunnel, or open framework structures, providing abundant active sites and diffusion channels for the reversible insertion / extraction of zinc ions. Simultaneously, vanadium exhibits multiple valence states (such as V... 5+ V 4+ V 3+ Vanadium undergoes abundant redox reactions during electrochemical processes, providing a high theoretical specific capacity. Furthermore, the relative abundance of vanadium resources makes vanadium-based cathode materials potentially low-cost and easily mass-producible.

[0004] However, challenges remain to be overcome in addressing issues such as structural stability, ion diffusion kinetics, and cycle life of vanadium-based materials. First, vanadium-based active materials dissolve to varying degrees into aqueous electrolytes during charge and discharge, leading to active material loss and continuous capacity decay, especially at low current densities. Second, divalent zinc ions, with their high charge density, exhibit strong electrostatic interactions with the vanadium-oxygen framework, resulting in relatively slow diffusion kinetics within the crystal lattice. Furthermore, the low intrinsic electronic conductivity of vanadium oxides limits the electrochemical performance of batteries at high rates.

[0005] Meanwhile, zinc anodes are prone to hydrogen evolution reaction (HER) and corrosion in aqueous electrolytes. HER is an electrochemical reduction process for hydrogen production, while corrosion is the chemical self-dissolution of zinc with water. Both consume active zinc, generate hydrogen gas, and cause the electrolyte pH to rise, which in turn leads to zinc surface passivation and dendrite growth, severely impairing the battery's reversibility, cycle life, and safety. Therefore, suppressing water-induced side reactions is key to improving battery performance.

[0006] To address the aforementioned problems, existing technologies offer several solutions. For example, CN113782727A discloses a method for preparing a zinc-ion battery doped cathode material, comprising: dissolving a vanadium source, an oxidant, a fuel, and a cation dopant in water and mixing them uniformly to obtain a mixed phase; and subjecting the mixed phase to a low-temperature combustion reaction to obtain the zinc-ion battery doped cathode material. The resulting zinc-ion battery doped cathode material exhibits higher conductivity, reduces the Coulomb resistance encountered during zinc ion insertion and extraction, and improves the zinc ion diffusion coefficient, thus contributing to improved electrochemical performance of zinc-ion batteries.

[0007] However, existing methods have limited effectiveness in improving the vanadium solubility, low electronic conductivity, and relatively slow diffusion kinetics of vanadium-based materials, thus restricting the improvement of the electrochemical performance of zinc-ion batteries. Therefore, it is necessary to provide a zinc-ion battery with excellent electrochemical performance. Summary of the Invention

[0008] In view of the above-mentioned technical problems existing in the prior art, the purpose of the present invention is to provide a zinc-ion battery and a method for preparing the same.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a zinc-ion battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte, characterized in that the positive electrode comprises a vanadium-based material, the vanadium-based material comprising vanadium pentoxide with water molecules and metal ions intercalated, and an MXene coating layer; the electrolyte comprises a zinc salt, water, and an additive, the additive having cations and anions, the anions having the structure shown in Formula I.

[0011] Formula I;

[0012] R1 and R2 are independently selected from H or C1~C10 alkyl groups.

[0013] In the zinc-ion battery of this invention, the electrochemical performance can be effectively improved by intercalating and coating vanadium pentoxide. Specifically, water molecules and metal ions are used to pre-intercalate vanadium pentoxide. The metal ions and water molecules can effectively widen the gap between the layers of the material, reduce the energy barrier for ion diffusion, and thus make the ion insertion / extraction process faster and more efficient. Moreover, the water molecules filling the spaces between the ion pillars stabilize the entire intercalation structure through a hydrogen bond network and also act as a shield for Zn. 2+The MXene coating layer interacts strongly with the vanadium pentoxide layers, reducing the diffusion barrier. It forms a continuous, efficient three-dimensional conductive network between the intercalated vanadium pentoxide particles, improving conductivity, reducing electrode internal resistance, and enhancing structural stability. This benefits the capacity utilization and cycle performance of zinc-ion batteries. Furthermore, the MXene material exhibits good flexibility, effectively immobilizing vanadium pentoxide particles and suppressing agglomeration and structural collapse during cycling. Based on these factors, zinc-ion batteries maintain excellent electrochemical performance even at high current densities.

[0014] However, during the discharge process of zinc-ion batteries, zinc ions are usually in the form of hydrated zinc ions ([Zn(H2O)6]). 2+ The vanadium-based material is embedded in the positive electrode in the form of a vanadium-oxygen framework (VO). These water molecules, especially the free water, hydrolyze with the vanadium-oxygen framework (VO), breaking the VO bonds and leading to vanadium dissolution and the dissolution of intercalated metal ions. This is more pronounced at low current densities. This invention effectively solves this problem by using an electrolyte adapted to the aforementioned vanadium-based material. The technical principle is as follows: During zinc-ion battery cycling, if the vanadium-based material undergoes structural dissolution leading to the dissolution of intercalated metal ions, the dithiocarbamate group in the additive can quickly recognize and capture the intercalated metal ions through two sulfur atoms, forming a stable cyclic complex. This complex then precipitates directly on the positive electrode surface, forming a stable and dense hydrophobic CEI layer in situ, effectively inhibiting further vanadium dissolution and intercalated ion dissolution. Moreover, unlike the mechanism in existing technologies where additive molecules form CEI precipitates through strong complexation with metal intercalated ions, the additive molecules in this invention react with Zn in the solution... 2+ Its coordination effect is relatively weak, therefore it can participate in the reconstruction of Zn through a relatively weak coordination effect. 2+ The solvated sheath structure undergoes a dynamic coordination-dissociation process at the interface, thereby continuously regulating the interfacial environment and further reducing the number of active water molecules at the negative electrode interface. Therefore, while preventing vanadium dissolution / metal ion dissolution on the positive electrode side, it can synergistically suppress interfacial hydrogen evolution and corrosion side reactions caused by the decomposition of active water molecules on the zinc negative electrode side, thus comprehensively improving the cycle life of zinc-ion batteries.

[0015] Taking copper ions as an example, the structure of the complex formed by the dithiocarbamate group and copper ions is shown in Formula II.

[0016] Formula II.

[0017] Preferably, the cation is selected from ammonium ion, sodium ion, dimethylammonium ion or diethylammonium ion.

[0018] Preferably, the additive includes at least one of ammonium dithiocarbamate, sodium dimethyl dithiocarbamate, dimethyl dimethyl dithiocarbamate, sodium diethyl dithiocarbamate, ammonium diethyl dithiocarbamate, diethyl dithiocarbamate, and sodium dibutyl dithiocarbamate.

[0019] Preferably, the bimetallic ion comprises a first metal ion and a second metal ion, wherein the first metal ion comprises bismuth and / or thallium, and the second metal ion comprises copper and / or silver. The first metal ion has a large ionic radius and, as a pillar ion, can effectively expand the interlayer spacing; the second metal ion is an excellent electronic conductor and, as a conductive ion, intercalates vanadium pentoxide, which can synergistically work with MXene material to construct an electron "highway," significantly improving the intrinsic electronic conductivity of the material and promoting rapid electron transport within the electrode.

[0020] Preferably, with the total molar amount of vanadium pentoxide intercalated by water molecules and metal ions being 100%, the molar content of the first metal ion is x, and the molar content of the second metal ion is y, where 1 ≤ x / y ≤ 9. For example, x / y can be 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, or 9, and preferably 2 ≤ x / y ≤ 8.

[0021] When x / y is too large, meaning there are too few conductive ions, the material cannot establish an efficient electronic conduction network, leading to increased electrode internal resistance and insufficient capacity. Simultaneously, while pillar ions have large atomic masses and do not contribute significantly to capacity, an excess of them can reduce the material's specific capacity. Conversely, when x / y is too small, meaning there are too many conductive ions, it can cause structural distortion, block ion channels, and compete with zinc ions for sites, resulting in capacity and cycling performance degradation. Furthermore, too few pillar ions cannot effectively expand the interlayer spacing, hindering zinc ion diffusion and weakening the stability of the layered structure, thus accelerating cycling capacity decay.

[0022] Preferably, x+y is 0.5~1, for example, it can be 0.5, 0.6, 0.7, 0.8, 0.9 or 1. Too high or too low a total concentration of intercalated ions is detrimental to their performance. Too few intercalated ions cannot effectively widen the interlayer spacing and improve the intrinsic conductivity of the material, and the resistance to zinc ion insertion / extraction remains relatively high. Excessive intercalated ions will over-occupy the interlayer space, hindering the diffusion channels of zinc ions, increasing the energy barrier for ion migration, and leading to deterioration of kinetic performance.

[0023] Preferably, the particle size of the vanadium pentoxide intercalated with water molecules and metal ions is in the range of 30 nm to 50 nm. Exemplarily, the particle size can be 30 nm, 32 nm, 35 nm, 38 nm, 40 nm, 43 nm, 46 nm, 48 nm, or 50 nm, etc.

[0024] The MXene material in the MXene coating layer includes Ti3C2T. x Ti2CT x and V2CT x At least one of them, wherein T x It refers to a functional group.

[0025] Preferably, the MXene coating layer accounts for 15% to 30% of the mass of the vanadium-based material, for example, 15%, 18%, 20%, 23%, 26%, 28%, or 30%. If the MXene content is too low, charge transport becomes a bottleneck, electrode reaction kinetics are sluggish, and the utilization rate of active materials is low; if the MXene content is too high, the excessive MXene will significantly reduce the overall discharge specific capacity of the electrode.

[0026] As a preferred embodiment of the zinc-ion battery of the present invention, the additive has a mass concentration of z g / L in the electrolyte, and x, y, and z satisfy the relationship: 2.4 ≤ (x+y) / z ≤ 5. For example, (x+y) / z can be 2.4, 2.6, 2.8, 3, 3.2, 3.5, 3.7, 4, 4.2, 4.4, 4.6, 4.8, or 5, etc. When x, y, and z satisfy the above formula, the cycle stability of the battery is significantly improved.

[0027] Preferably, 0.1≤z≤0.3. For example, z can be 0.1, 0.15, 0.2, 0.25 or 0.3, etc., and preferably 0.15≤z≤0.25.

[0028] As a preferred technical solution for the zinc-ion battery of the present invention, the preparation method of the vanadium-based material includes the following steps:

[0029] S1. Vanadium pentoxide, oxidant, surfactant, first intercalating agent and second intercalating agent are mixed evenly in an aqueous acid solution to obtain a mixed solution. The mixed solution is subjected to a hydrothermal reaction to obtain vanadium pentoxide with water molecules and metal ions intercalated.

[0030] The first intercalating agent contains the first metal ion, and the second intercalating agent contains the second metal ion;

[0031] S2. After mixing the vanadium pentoxide with water molecules and metal ions intercalated with it and a dispersion containing MXene, freeze-dry the mixture to obtain the vanadium-based material.

[0032] In the preparation method of this invention, under the action of surfactant and acid, a hydrothermal method is used to intercalate water molecules and metal ions into vanadium pentoxide. The surfactant adsorbs on the surface of the newly formed crystal nuclei, forming a protective layer that physically hinders the contact and merging between crystal nuclei, limiting the further growth of nanoparticles. This results in spherical nanoparticles with uniform morphology and small particle size. The smaller nanoparticle size is beneficial for maintaining a high specific surface area and increasing electrochemical active sites. Furthermore, the nanoparticles are mixed with a dispersion of MXene and then freeze-dried to prepare a two-dimensional heterostructure material of MXene-coated vanadium oxide nanoparticles. The freeze-drying method avoids the dehydration reaction caused by high temperature, ensuring the intercalation effect of water molecules. At the same time, the flexibility and abundant functional groups on the surface of MXene can effectively "anchor" the nanoparticles on its surface and between layers, inhibiting their aggregation.

[0033] Preferably, the oxidant is hydrogen peroxide, and the volume ratio of water to hydrogen peroxide is 5 to 15, for example, it can be 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5 or 15, etc.

[0034] Preferably, the surfactant comprises hexadecyltrimethylammonium bromide and / or sodium dodecyl sulfate.

[0035] Preferably, the mass concentration of the surfactant is 2 g / L to 5 g / L, for example, it can be 2 g / L, 2.5 g / L, 3 g / L, 3.5 g / L, 4 g / L, 4.5 g / L or 5 g / L.

[0036] Preferably, the aqueous solution of the acid is dilute nitric acid, and the molar concentration of the dilute nitric acid is 0.05-1.0 mol / L, for example, it can be 0.05 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, or 1.0 mol / L. Preferably, the first intercalating agent includes at least one selected from acetate, nitrate, or sulfate.

[0037] Preferably, the second intercalating agent comprises at least one of acetate, nitrate, or sulfate.

[0038] Preferably, the ratio of the molar amount of vanadium pentoxide to the sum of the molar amounts of metal ions in the first intercalating agent and the metal ions in the second intercalating agent is 1 to 2, for example, it can be 1, 1.2, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 or 2, etc.

[0039] Preferably, the molar concentration of vanadium pentoxide in the mixed solution is 20 mmol / L to 50 mmol / L, for example, it can be 20 mmol / L, 22 mmol / L, 25 mmol / L, 28 mmol / L, 30 mmol / L, 33 mmol / L, 36 mmol / L, 38 mmol / L, 40 mmol / L, 42 mmol / L, 45 mmol / L, 48 mmol / L or 50 mmol / L, etc.

[0040] Preferably, the temperature of the hydrothermal reaction is 160℃~200℃, for example, it can be 160℃, 165℃, 170℃, 175℃, 180℃, 185℃, 190℃, 195℃ or 200℃.

[0041] Preferably, the hydrothermal reaction time is 12h to 20h, for example, it can be 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h or 20h.

[0042] Preferably, the freeze-drying temperature is -60℃ to -30℃, for example, it can be -60℃, -55℃, -50℃, -45℃, -40℃, -35℃, or -30℃. The freeze-drying time is 24h to 50h, for example, it can be 24h, 26h, 28h, 30h, 33h, 35h, 38h, 40h, 42h, 45h, 47h, or 50h.

[0043] As a preferred technical solution of the zinc-ion battery of the present invention, the zinc salt in the electrolyte includes at least one of zinc sulfate, zinc acetate, zinc perchlorate, zinc trifluoromethanesulfonate and zinc tetrafluoroborate, preferably zinc sulfate.

[0044] Preferably, the concentration of the zinc salt in the electrolyte is 0.5 mol / L to 3 mol / L, for example, it can be 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L or 3 mol / L.

[0045] In a second aspect, the present invention provides a method for preparing a zinc-ion battery as described in the first aspect, comprising the following steps:

[0046] A zinc-ion battery is formed by stacking or winding a positive electrode, a negative electrode, and a separator, injecting an electrolyte into the battery cell, and then encapsulating it.

[0047] Compared with existing technologies, the present invention has the following beneficial effects:

[0048] In the zinc-ion battery of this invention, the intercalation of vanadium pentoxide and the coating of MXene by water molecules and metal ions, combined with an electrolyte of a specific composition, not only facilitate rapid ion insertion / extraction, enhancing the intrinsic conductivity of the material and stabilizing the material structure, but also synergistically suppress interfacial hydrogen evolution and corrosion side reactions caused by the decomposition of active water molecules on the zinc anode side, while preventing vanadium dissolution / metal ion leaching on the positive electrode side. The combined effect of these factors results in excellent electrochemical performance in the zinc-ion battery. Detailed Implementation

[0049] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0050] The specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0051] In this embodiment of the invention, dilute nitric acid refers to an aqueous solution of nitric acid.

[0052] In the following examples, the mass concentration of the additive in the electrolyte is denoted as z g / L. For example, when the mass concentration of the additive in the electrolyte is 0.2 g / L, then z = 0.2.

[0053] Example 1

[0054] This embodiment provides a zinc-ion battery, including a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode includes a vanadium-based material, which comprises vanadium pentoxide with water molecules and metal ions (wherein the first metal ion is Bi ions and the second metal ion is Cu ions) intercalated, and an MXene coating layer. Taking the total molar amount of the water molecules and metal ion intercalated vanadium pentoxide as 100%, the molar content x of the first metal ion (Bi ions) is 0.48, and the molar content y of the second metal ion (Cu ions) is 0.12, then x / y = 4; the MXene coating layer accounts for 20% of the mass of the vanadium-based material.

[0055] The electrolyte comprises zinc salt, water, and an additive, wherein the additive is sodium dimethyl dithiocarbamate, and the mass concentration of the additive in the electrolyte is 0.2 g / L.

[0056] This embodiment also provides a method for preparing the above-mentioned zinc-ion battery, including the following steps:

[0057] (1) Preparation of vanadium-based cathode materials:

[0058] S1: Weigh 3 mmol of commercial V₂O₅ powder, 1.44 mmol of bismuth nitrate, 0.36 mmol of copper acetate, and 0.3 g of surfactant (hexadecyltrimethylammonium bromide, CTAB). Add the above raw materials to 90 ml of 0.3 mol / L dilute nitric acid and stir until homogeneous. Then add 10 ml of hydrogen peroxide and stir until homogeneous to obtain a mixed solution. Transfer the mixed solution to a polytetrafluoroethylene autoclave and heat at 180 °C for 18 hours to obtain nano-vanadium oxide (Bi₂O₅) with co-intercalated water molecules, bismuth ions, and copper ions. 0.48 Cu 0.12 V2O5·nH2O).

[0059] S2: The obtained nano-vanadium oxide is reacted with Ti3C2T x The MXene colloidal solution was uniformly mixed, and then the suspension was freeze-dried at -55°C for 48 hours to obtain an MXene-coated two-dimensional heterostructure material, denoted as Bi. 0.48 Cu 0.12 V2O5·nH2O / MXene.

[0060] (2) Preparation of the positive electrode:

[0061] Bi 0.48 Cu 0.12 V2O5·nH2O / MXene was used as the positive electrode active material. The positive electrode active material was mixed with Super P and PVDF in NMP at a mass ratio of 8:1:1 to obtain a positive electrode slurry. The positive electrode slurry was coated on the surface of titanium foil and dried to obtain the positive electrode.

[0062] (3) Preparation of electrolyte:

[0063] In an air atmosphere, using deionized water as a solvent and zinc sulfate heptahydrate as a zinc salt, first prepare 100 mL of zinc sulfate electrolyte with a concentration of 2 mol / L, then add 20 mg of sodium dimethyl dithiocarbamate to it, and stir evenly until the additive is completely dissolved to obtain the electrolyte.

[0064] (4) The above-mentioned positive electrode is stacked with GF / D separator and zinc foil in sequence to form a cell, with GF / D separator located between the positive electrode and modified zinc negative electrode. Electrolyte is then injected into the cell and packaged as CR2032 button cell.

[0065] Thanks to the confinement effect of hexadecyltrimethylammonium bromide, spherical nanoparticles with a diameter of approximately 40 nm and uniform morphology were obtained. This is beneficial for maintaining a high specific surface area while exposing more active sites. However, since MXene has not yet been added, the nanoparticles will spontaneously approach each other, aggregate, and fuse into larger and more stable particles in order to reduce surface energy and tend to stabilize. This further verifies the necessity of adding MXene in step S2. The flexibility and abundant surface functional groups of MXene can effectively "anchor" the nanoparticles to their surface and interlayer through interactions, inhibiting their aggregation.

[0066] Example 2

[0067] The difference from Example 1 is that the amount of bismuth nitrate was changed to 2.4 mmol and the amount of copper acetate was changed to 0.6 mmol, while all other steps and parameters remained unchanged.

[0068] In the vanadium-based material of this embodiment, with the total molar amount of vanadium pentoxide intercalated by water molecules and metal ions being 100%, the molar content of Bi ions x is 0.8, and the molar content of Cu ions y is 0.2, then x + y = 1.

[0069] Example 3

[0070] The difference from Example 1 is that the amount of bismuth nitrate is changed to 1.2 mmol and the amount of copper acetate is changed to 0.3 mmol, while all other steps and parameters remain unchanged.

[0071] In the vanadium-based material of this embodiment, with the total molar amount of vanadium pentoxide intercalated by water molecules and metal ions being 100%, the molar content of Bi ions x is 0.4, and the molar content of Cu ions y is 0.1, then x + y = 0.5.

[0072] Example 4

[0073] The difference from Example 1 is that the amount of bismuth nitrate was changed to 3.2 mmol and the amount of copper acetate was changed to 0.8 mmol, while all other steps and parameters remained unchanged.

[0074] In the vanadium-based material of this embodiment, with the total molar amount of vanadium pentoxide intercalated by water molecules and metal ions being 100%, the molar content of Bi ions x is 1.067, and the molar content of Cu ions y is 0.267, then x + y = 1.334.

[0075] Example 5

[0076] The difference from Example 1 is that the amount of bismuth nitrate is changed to 0.4 mmol and the amount of copper acetate is changed to 0.1 mmol, while all other steps and parameters remain unchanged.

[0077] In the vanadium-based material of this embodiment, taking the total molar amount of vanadium pentoxide intercalated by water molecules and metal ions as 100%, the molar content of Bi ions x is 0.133, and the molar content of Cu ions y is 0.033, then x + y = 0.166.

[0078] Example 6

[0079] The difference from Example 1 is that the amount of sodium dimethyl dithiocarbamate was changed to 15 mg, while all other steps and parameters remained unchanged.

[0080] In this embodiment, the additive in the electrolyte is sodium dimethyl dithiocarbamate, and the mass concentration of the additive in the electrolyte is 0.15 g / L.

[0081] Example 7

[0082] The difference from Example 1 is that the amount of sodium dimethyl dithiocarbamate was changed to 25 mg, while all other steps and parameters remained unchanged.

[0083] In this embodiment, the additive in the electrolyte is sodium dimethyl dithiocarbamate, and the mass concentration of the additive in the electrolyte is 0.25 g / L.

[0084] Example 8

[0085] The difference from Example 1 is that the amount of MXene is changed so that the mass percentage of the MXene coating layer in the vanadium-based material is 15%, while the other steps and parameters remain unchanged.

[0086] Example 9

[0087] The difference from Example 1 is that the amount of MXene is changed so that the mass ratio of the MXene coating layer in the vanadium-based material is 30%, while the other steps and parameters remain unchanged.

[0088] Example 10

[0089] The difference from Example 1 is that the amount of MXene is changed so that the mass ratio of the MXene coating layer in the vanadium-based material is 40%, while the other steps and parameters remain unchanged.

[0090] Example 11

[0091] The difference from Example 1 is that the amount of MXene is changed so that the mass percentage of the MXene coating layer in the vanadium-based material is 5%, while the other steps and parameters remain unchanged.

[0092] Example 12

[0093] The difference from Example 1 is that the amount of bismuth nitrate is changed to 1.2 mmol and the amount of copper acetate is changed to 0.6 mmol, while all other steps and parameters remain unchanged.

[0094] In the vanadium-based material of this embodiment, with the total molar amount of vanadium pentoxide intercalated by water molecules and metal ions being 100%, the molar content of Bi ions x is 0.4, and the molar content of Cu ions y is 0.2, then x / y = 2.

[0095] Example 13

[0096] The difference from Example 1 is that the amount of bismuth nitrate is changed to 1.6 mmol and the amount of copper acetate is changed to 0.2 mmol, while all other steps and parameters remain unchanged.

[0097] In the vanadium-based material of this embodiment, with the total molar amount of vanadium pentoxide intercalated by water molecules and metal ions being 100%, the molar content of Bi ions x is 0.533, and the molar content of Cu ions y is 0.067, then x / y = 8.

[0098] Example 14

[0099] The difference from Example 1 is that bismuth nitrate is replaced with thallium sulfate, the molar amount of bismuth is the same as that of thallium, and all other steps and parameters remain unchanged.

[0100] The vanadium-based material in this embodiment includes vanadium pentoxide with water molecules and metal ions (Tl and Cu) intercalated, as well as an MXene coating layer.

[0101] Example 15

[0102] The difference from Example 1 is that copper acetate is replaced with silver nitrate, the molar amount of copper is the same as that of silver, and all other steps and parameters remain unchanged.

[0103] The vanadium-based material in this embodiment includes vanadium pentoxide with water molecules and metal ions (Bi and Ag) intercalated, and an MXene coating layer.

[0104] Example 16

[0105] The difference from Example 1 is that the additive in the electrolyte is replaced with sodium diethyldithiocarbamate, while all other steps and parameters remain unchanged.

[0106] Example 17

[0107] The difference from Example 1 is that the amount of sodium dimethyl dithiocarbamate was changed to 30 mg, while all other steps and parameters remained unchanged.

[0108] In this embodiment, the additive in the electrolyte is sodium dimethyl dithiocarbamate, and the mass concentration of the additive in the electrolyte is 0.3 g / L, so (x+y) / z=2.

[0109] Example 18

[0110] The difference from Example 1 is that the amount of sodium dimethyl dithiocarbamate was changed to 10.9 mg, while all other steps and parameters remained unchanged.

[0111] In this embodiment, the additive in the electrolyte is sodium dimethyl dithiocarbamate, and the mass concentration of the additive in the electrolyte is 0.109 g / L, so (x+y) / z=5.5.

[0112] Example 19

[0113] The difference from the preparation method in Example 1 is that the amount of bismuth nitrate and copper acetate is changed to 0.9 mmol, while all other steps and parameters remain unchanged.

[0114] In the vanadium-based material of this embodiment, with the total molar amount of vanadium pentoxide intercalated by water molecules and metal ions being 100%, the molar content of Bi ions x is 0.3, and the molar content of Cu ions y is 0.3, then x / y = 1.

[0115] Example 20

[0116] The difference from Example 1 is that the amount of bismuth nitrate was changed to 1.62 mmol and the amount of copper acetate was changed to 0.18 mmol, while all other steps and parameters remained unchanged.

[0117] In the vanadium-based material of this embodiment, with the total molar amount of vanadium pentoxide intercalated by water molecules and metal ions being 100%, the molar content of Bi ions x is 0.54, and the molar content of Cu ions y is 0.06, then x / y = 9.

[0118] Example 21

[0119] The difference from Example 1 is that the amount of bismuth nitrate is changed to 1.8 mmol and the amount of copper acetate is changed to 0 mmol, while all other steps and parameters remain unchanged.

[0120] In the vanadium-based material of this embodiment, with the total molar amount of vanadium pentoxide intercalated by water molecules and metal ions being 100%, the molar content of Bi ions x is 0.6, and the molar content of Cu ions y is 0.

[0121] Example 22

[0122] The difference from Example 1 is that the amount of bismuth nitrate is changed to 0 mmol and the amount of copper acetate is changed to 1.8 mmol, while all other steps and parameters remain unchanged.

[0123] In the vanadium-based material of this embodiment, with the total molar amount of vanadium pentoxide intercalated by water molecules and metal ions being 100%, the molar content x of Bi ions is 0, and the molar content y of Cu ions is 0.6.

[0124] Comparative Example 1

[0125] The difference from Example 1 is that Bi ion and Cu ion intercalation was not used.

[0126] Comparative Example 2

[0127] The difference from Example 1 is that the amount of sodium dimethyl dithiocarbamate was changed to 0 mg, while all other steps and parameters remained unchanged.

[0128] Comparative Example 3

[0129] The difference from Example 1 is that the freeze-dried product was calcined at 300°C for 2 hours under a protective atmosphere to remove the intercalated water of crystallization.

[0130] Comparative Example 4

[0131] The difference from Example 1 is that the additive is replaced with ethylenediaminetetraacetic acid (EDTA).

[0132] Electrochemical performance tests were performed on the zinc-ion batteries of each embodiment and comparative example:

[0133] (1) Low-rate cycling performance test: The temperature is 25℃, the charge / discharge rate is 0.5A / g, and the number of cycles is 500. The initial specific capacity C1 of 0.5 A / g and the specific capacity C2 after 500 cycles of 0.5 A / g are obtained. The capacity retention rate after 500 cycles of 0.5 A / g is calculated based on C1 and C2. The calculation formula is: capacity retention rate after 500 cycles of 0.5 A / g C2 / C1×100%.

[0134] (2) High-rate cycling performance test: The temperature is 25℃, the charge / discharge rate is 5A / g, and the number of cycles is 4000. The initial specific capacity C3 of 5A / g and the specific capacity C4 after 500 cycles of 5A / g are obtained. The capacity retention rate after 4000 cycles of 5A / g is calculated based on C3 and C4. The calculation formula is: capacity retention rate after 4000 cycles of 5A / g C4 / C3×100%.

[0135] (3) The zinc-ion battery was subjected to 500 charge-discharge cycles at a temperature of 25°C and a charge-discharge rate of 0.5 A / g. After the cycles, the concentration of vanadium in the electrolyte was determined by ICP-OES. The results are shown in Table 2. As can be seen from Table 2, the present invention can form a dense CEI film and reduce vanadium dissolution by using modified vanadium pentoxide in combination with a specific electrolyte.

[0136]

[0137]

[0138] Note: In Table 1, x represents the molar content of the first metal ion and y represents the molar content of the second metal ion.

[0139]

[0140]

[0141] In summary, the zinc-ion battery of this invention, through the intercalation of vanadium pentoxide and the coating of MXene with water molecules and metal ions, and in synergy with an electrolyte of a specific composition, not only facilitates rapid ion insertion / extraction, enhances the intrinsic conductivity of the material, and stabilizes the material structure, but also, while preventing vanadium dissolution / metal ion leaching on the positive electrode side, synergistically suppresses interfacial hydrogen evolution and corrosion side reactions caused by the decomposition of active water molecules on the zinc negative electrode side. The combined effect of these factors results in the zinc-ion battery exhibiting excellent electrochemical performance.

[0142] Meanwhile, a comparison of Examples 1, 4-5, and Comparative Example 1 shows that by introducing intercalation ions, the interlayer spacing of the material can be increased, the intrinsic conductivity of the material can be improved, and thus the kinetic performance of the material can be improved. However, both excessively high and excessively low total concentrations of intercalation ions are not conducive to their full performance. Too few intercalation ions cannot effectively increase the interlayer spacing and improve the intrinsic conductivity of the material, and the resistance to zinc ion insertion / extraction is still relatively large. Excessive intercalation ions will occupy the interlayer space excessively, which will hinder the diffusion channels of zinc ions, increase the energy barrier for ion migration, and lead to deterioration of kinetic performance.

[0143] A comparison of Example 1 with Examples 10 and 11 shows that the preferred MXene content is 15% to 30%. Too high or too low a content will negatively impact the overall battery performance. If the MXene content is too low, charge transport becomes a bottleneck, electrode reaction kinetics are sluggish, and the utilization rate of active materials is low. If the MXene content is too high, excessive MXene will significantly reduce the overall discharge specific capacity of the electrode.

[0144] A comparison of Example 1 and Examples 17-18 shows that (x+y) / z within the preferred range of 2.4 to 5 is more conducive to improving the electrochemical performance of zinc-ion batteries.

[0145] A comparison of Examples 1 with Examples 19, 20, 21, and 22 shows that, compared to intercalation using only the first metal ion (Example 21) or only the second metal ion (Example 22), synergistic intercalation of both can improve the performance of vanadium-based materials. Furthermore, the content of the first and second metal ions within a preferred range can achieve synergistic effects. The first metal ion acts as the pillar ion, and the second metal ion acts as the conducting ion. When x / y is too large, i.e., too few conducting ions, the material cannot establish an efficient electronic conduction network, leading to increased electrode resistance and insufficient capacity. Simultaneously, the pillar ion has a large atomic mass and does not contribute significantly to capacity; excessive pillar ions can reduce the material's specific capacity. When x / y is too small, i.e., too many conducting ions, structural distortion occurs, ion channels are blocked, and zinc ions compete for sites, leading to capacity and cycling performance degradation. Furthermore, too few pillar ions cannot effectively expand the interlayer spacing, making zinc ion diffusion difficult and weakening the stability of the layered structure, thus accelerating cycling capacity decay.

[0146] The comparison between Example 1 and Comparative Example 2 shows that without introducing sodium dimethyl dithiocarbamate into the electrolyte, modifying the cathode material alone cannot synergistically improve the electrochemical performance of zinc-ion batteries.

[0147] A comparison between Example 1 and Comparative Example 3 shows that high-temperature calcination leads to dehydration, resulting in the absence of anhydrous molecule intercalation in the vanadium-based material. This causes a significant decrease in the performance of the zinc-ion battery. This is because water molecules fill the spaces between the ion pillars, stabilizing the entire intercalation structure through a hydrogen bond network and acting as a shield for Zn. 2+ The strong electrostatic interaction with the layers and the reduction of the diffusion barrier play a crucial role in improving the performance of zinc-ion batteries.

[0148] A comparison between Example 1 and Comparative Example 4 shows that ethylenediaminetetraacetic acid (EDTA), as a commonly used complexing agent, has a different mechanism of action than that of this application and cannot synergistically enhance the electrochemical performance of zinc-ion batteries with intercalated vanadium-based materials.

[0149] The applicant declares that the detailed method of the present invention is illustrated by the above embodiments, but the present invention is not limited to the above detailed method, that is, it does not mean that the present invention must rely on the above detailed method to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A zinc-ion battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, characterized in that, The positive electrode comprises a vanadium-based material, which includes vanadium pentoxide with water molecules and metal ions intercalated, and an MXene coating layer; the electrolyte comprises a zinc salt, water, and an additive, the additive having both cations and anions, the anion having the structure shown in Formula I. Formula I; R1 and R2 are independently selected from H or C1~C10 alkyl groups.

2. The zinc-ion battery according to claim 1, characterized in that, The cation is selected from ammonium ion, sodium ion, dimethylammonium ion or diethylammonium ion; Preferably, the additive includes at least one of ammonium dithiocarbamate, sodium dimethyl dithiocarbamate, dimethyl dimethyl dithiocarbamate, sodium diethyl dithiocarbamate, ammonium diethyl dithiocarbamate, diethyl dithiocarbamate, and sodium dibutyl dithiocarbamate.

3. The zinc-ion battery according to claim 1 or 2, characterized in that, The metal ions include a first metal ion and a second metal ion, wherein the first metal ion includes bismuth and / or thallium, and the second metal ion includes copper and / or silver; Preferably, with the total molar amount of vanadium pentoxide intercalated by water molecules and metal ions being 100%, the molar content of the first metal ion is x, the molar content of the second metal ion is y, 1≤x / y≤9, and more preferably 2≤x / y≤8; Preferably, x+y is 0.5~1; Preferably, the particle size of the vanadium pentoxide intercalated with water molecules and metal ions is in the range of 30 nm to 50 nm.

4. The zinc-ion battery according to any one of claims 1-3, characterized in that, The MXene material in the MXene coating layer includes Ti3C2T. x Ti2CT x and V2CT x At least one of them, wherein T x Indicates a functional group; Preferably, the MXene coating layer accounts for 15% to 30% of the mass of the vanadium-based material.

5. The zinc-ion battery according to any one of claims 1-4, characterized in that, The mass concentration of the additive in the electrolyte is z g / L, and x, y and z satisfy the relationship: 2.4≤(x+y) / z≤5; Preferably, 0.1≤z≤0.3, and more preferably 0.15≤z≤0.

25.

6. The zinc-ion battery according to any one of claims 1-5, characterized in that, The preparation method of the vanadium-based material includes the following steps: S1. Vanadium pentoxide, oxidant, surfactant, first intercalating agent and second intercalating agent are mixed evenly in an aqueous acid solution to obtain a mixed solution. The mixed solution is subjected to a hydrothermal reaction to obtain vanadium pentoxide with water molecules and metal ions intercalated. The first intercalating agent contains the first metal ion, and the second intercalating agent contains the second metal ion; S2. After mixing the vanadium pentoxide with water molecules and metal ions intercalated with it and a dispersion containing MXene, freeze-dry the mixture to obtain the vanadium-based material.

7. The zinc-ion battery according to claim 6, characterized in that, The oxidant is hydrogen peroxide, and the volume ratio of water to hydrogen peroxide is 5-15. Preferably, the surfactant comprises hexadecyltrimethylammonium bromide and / or sodium dodecyl sulfate; Preferably, the mass concentration of the surfactant is 2 g / L to 5 g / L; Preferably, the aqueous solution of the acid is dilute nitric acid, and the molar concentration of the dilute nitric acid is 0.05-1.0 mol / L; Preferably, the first intercalating agent comprises at least one of acetate, nitrate, or sulfate; Preferably, the second intercalating agent comprises at least one selected from acetate, nitrate, or sulfate; Preferably, the ratio of the molar amount of vanadium pentoxide to the sum of the molar amounts of metal ions in the first intercalating agent and intercalating ions in the second intercalating agent is 1 to 2. Preferably, the molar concentration of vanadium pentoxide in the mixed solution is 20 mmol / L to 50 mmol / L.

8. The zinc-ion battery according to any one of claims 1-7, characterized in that, The temperature of the hydrothermal reaction is 160℃~200℃; Preferably, the hydrothermal reaction time is 12h~20h; Preferably, the freeze-drying temperature is -60℃ to -30℃, and the freeze-drying time is 24h to 50h.

9. The zinc-ion battery according to any one of claims 1-8, characterized in that, The zinc salt in the electrolyte includes at least one of zinc sulfate, zinc acetate, zinc perchlorate, zinc trifluoromethanesulfonate, and zinc tetrafluoroborate, preferably zinc sulfate; Preferably, the concentration of the zinc salt in the electrolyte is 0.5 mol / L to 3 mol / L.

10. A method for preparing a zinc-ion battery as described in any one of claims 1-9, characterized in that, The preparation method includes the following steps: A zinc-ion battery is formed by stacking or winding a positive electrode, a negative electrode, and a separator, injecting an electrolyte into the battery cell, and then encapsulating it.

Images