Organic positive electrode material based on naphthoquinone, preparation method of organic positive electrode material and application of organic positive electrode material in aqueous zinc ion battery

Abstract

The invention relates to the technical field of electrochemical energy storage, in particular to an organic positive electrode material based on naphthoquinone, a preparation method of the organic positive electrode material and application of the organic positive electrode material in an aqueous zinc ion battery. The positive electrode material comprises an organic matter and carbon powder, the organic matter is one of naphthoquinone, menadione and 2-hydroxy-1, 4-naphthoquinone; the carbon powder is functionalized carbon powder or unfunctionalized carbon powder. The inherent porosity and electronegative carbonyl of the functionalized carbon powder are beneficial to enhancing the reaction activity of the positive electrode material, a proton-rich region is constructed around organic molecules, the problem of slow charge transfer existing in a positive electrode / electrolyte interface for a long time is solved, and the cycling stability and reaction kinetics of the material are improved while the proton storage capacity is promoted. Meanwhile, the organic matter positive electrode can effectively catalyze the conversion reaction of I- / I0, anchor the polyiodide ions, inhibit the shuttle side reaction of the polyiodide ions and reduce the growth of zinc dendrites, so that the specific capacity and the cycling stability of the aqueous zinc-iodine battery are remarkably improved.

Description

Technical Field

[0001] This application relates to the technical field of electrochemical energy storage, and particularly relates to an organic cathode material based on naphthoquinone, a preparation method thereof, and uses thereof in aqueous zinc-ion batteries. Background Art

[0002] With the continuous growth of the demand for renewable energy in daily life, due to their inherent safety, low cost, and high theoretical capacity, aqueous zinc-ion batteries have become a promising supplement or alternative to traditional lithium-ion batteries. However, the repeated insertion and extraction of hydrated Zn 2+ usually lead to the structural collapse of inorganic hosts, resulting in serious capacity decay and even battery failure problems during the cycling process of zinc-ion batteries. Compared with inorganic substances, organic cathode materials with flexible structures and adjustable structures can effectively buffer the volume changes and electrostatic interactions caused by the insertion of hydrated Zn 2+ Therefore, organic cathode materials often have better structural stability and cycle life.

[0003] For polymers such as polyaniline and polypyrrole, as well as organic small molecules containing amino and sulfhydryl groups, benzoquinone-based organic compounds have become a research hotspot for organic battery materials due to their high reactivity and low cost. However, the problems of low conductivity and molecular solubility existing in benzoquinone-based materials greatly limit the fast charging ability and self-discharge performance of aqueous zinc-organic batteries. More seriously, the slow charge migration and electrode internal diffusion kinetics of zinc ions at the cathode-electrolyte interface (CEI) exacerbate the slow rate performance and reaction reversibility of zinc-organic batteries. Compared with zinc ions, protons with smaller ionic radii and charges have lower ionic migration barriers and diffusion rates, which are beneficial to improving the reaction kinetics of organic cathodes. In addition, the introduction of a double benzene ring naphthoquinone structure can significantly increase its own conductivity while reducing the material solubility and improving the stability of organic cathodes. Therefore, constructing organic molecules with a fast proton deintercalation reaction mechanism is an important strategy to promote the development of aqueous zinc-organic batteries.

[0004] It should be noted that most quinone organic molecules as cathode materials have the problem of low working voltage (<0.8V), which seriously hinders the construction of high-energy-density aqueous zinc batteries. Benefiting from advantages such as high abundance, low toxicity, and high redox potential (~1.3V), aqueous zinc-iodine batteries based on iodine or iodide ions as active materials have broad application prospects in the field of electrochemical energy storage. Currently, aqueous zinc-iodine batteries mainly face problems such as slow iodine / iodide ion conversion reactions and polysulfide ion shuttling. In particular, organic composites have become one of the most promising catalytic cathode materials for zinc-iodine batteries due to their low cost, diverse structures, and environmental friendliness. Compared with a large number of carbon materials adsorbing or electrodepositing iodine as cathode materials, using a naphthoquinone-type organic cathode with high reactivity as an efficient iodine / iodide ion reaction catalyst can effectively promote the conversion efficiency of iodine / iodide ions. At the same time, it can inhibit the formation and shuttling side reactions of polysulfide ions, and construct an electrolytic zinc-iodine battery with both high specific capacity and stability. Therefore, in view of the problems of slow kinetics, serious self-discharge, limited cycle life, and low Coulomb efficiency faced by organic cathodes in zinc-ion batteries, this application is proposed. Summary of the Invention

[0005] The technical solution of this application is as follows:

[0006] In the first aspect of this application, an aromatic-based organic cathode material is provided, and the cathode material includes: an organic substance and carbon powder;

[0007] The organic substance is one of naphthoquinone, methylnaphthoquinone, and 2-hydroxy-1,4-naphthoquinone;

[0008] The carbon powder is selected from one of graphene, activated carbon, or carbon nanotubes.

[0009] The carbon powder is functionalized carbon powder or non-functionalized carbon powder;

[0010] The functionalized carbon powder is carboxylated carbon powder or hydroxylated carbon powder.

[0011] Preferably, the cathode material further contains a conductive agent and a binder, and the mass ratio of the organic substance, carbon powder, conductive agent, and binder is (4~8):(5~0.5):(1~0.5):1.

[0012] For example, 4.5:5:0.5:1, 5:3.5:0.5:1, 6.5:2:0.5:1, 8:0.5:0.5:1.

[0013] Among them, the organic substance is uniformly embedded in the carbon powder, for example, the organic substance is uniformly embedded in functionalized porous activated carbon.

[0014] The second aspect of the present application provides a preparation method of the aromatic-based organic cathode material described in the first aspect, and the preparation method includes the following steps:

[0015] Mix the cathode material precursor containing the organic matter and carbon powder, physically grind it, and add an organic solvent to mix to obtain a slurry;

[0016] Coat the obtained slurry on the current collector, and the cathode material can be obtained after drying treatment;

[0017] The organic matter is one of naphthoquinone, menadione, and 2-hydroxy-1,4-naphthoquinone;

[0018] The carbon powder is selected from one of graphene, activated carbon, or carbon nanotubes;

[0019] The carbon powder is functionalized carbon powder or non-functionalized carbon powder;

[0020] The functionalized carbon powder is carboxylated carbon powder or hydroxylated carbon powder.

[0021] Specifically, for example, the functionalized carbon powder is: carboxylated porous activated carbon or hydroxylated porous activated carbon.

[0022] For example: through the grinding process, the organic matter is evenly embedded into the negatively charged porous activated carbon, thereby exposing more organic host active sites and improving the reaction activity.

[0023] Preferably, the cathode material precursor further includes: a conductive agent and a binder.

[0024] Preferably, the preparation method of the functionalized carbon powder is as follows:

[0025] Add activated carbon to 2 - 5.0 mol / l nitric acid to obtain solution A, wherein the mass-volume ratio of carbon powder to nitric acid is 1:5 - 1:10.

[0026] Place solution A in a sealed autoclave, carry out hydrothermal treatment at 140 - 180 °C for 6 - 12 hours to obtain solution B, and perform solid-liquid separation to obtain the functionalized carbon powder.

[0027] Preferably, the mass ratio of the organic matter, carbon powder, conductive agent, and binder is (4 - 7):(4 - 1.5):(1 - 0.5):1.

[0028] Preferably, the organic solvent is selected from one or more of N-methylpyrrolidone, dimethyl sulfoxide, and acetonitrile.

[0029] Coat or roll the obtained slurry evenly onto the current collector, and dry it to obtain the cathode material.

[0030] Preferably, the loading amount of the positive electrode material on the current collector is 2.0 to 30.0 mg cm -2 .

[0031] Preferably, the current collector is selected from one or more of carbon cloth, graphite paper, stainless steel mesh, stainless steel foil, titanium mesh, and titanium foil.

[0032] The drying condition is drying at 60 °C - 80 °C for 8 - 24 hours.

[0033] Preferably, the binder is selected from one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC).

[0034] The third aspect of the present application provides an aqueous zinc-ion battery comprising the positive electrode material according to any one of the first aspect.

[0035] Preferably, the molar concentration of the zinc salt in the electrolyte is 0.5 - 5 M. The aqueous zinc-ion battery at this time can be called a zinc-naphthoquinone battery.

[0036] The fourth aspect of the present application provides an aqueous zinc-iodine battery comprising the positive electrode material according to any one of the first aspect.

[0037] Preferably, the molar concentration of the zinc salt in the electrolyte is 0.5 - 5 M, and the molar concentration of the iodine salt is 0.05 - 2 M. The aqueous zinc-ion battery at this time can be called a zinc-iodine battery.

[0038] Preferably, when assembling the battery, a suitable electrolyte is added according to the size of the battery, and the amount of the added electrolyte is 50 - 300 μL / g.

[0039] Preferably, the negative electrode sheet of the battery is a metal zinc foil, the thickness of the metal zinc foil is 30 - 100 μm, and it is sealed and assembled into a CR2032 battery under a pressure of 50 - 70 MPa for electrochemical performance testing.

[0040] The electrolyte of the battery is an aqueous solution of a zinc salt.

[0041] Preferably, the zinc salt is zinc sulfate heptahydrate, zinc trifluoromethanesulfonate, or zinc chloride.

[0042] Preferably, the molar concentration of the zinc salt is 0.5 - 5 M.

[0043] Preferably, the zinc salt is zinc sulfate heptahydrate, zinc trifluoromethanesulfonate, or zinc chloride.

[0044] Preferably, in the aqueous zinc-iodine battery, the iodine salt is one or more of ammonium iodide, zinc iodide, potassium iodide, sodium iodide, manganese iodide, iodine bromide, and some iodine ion complexes.

[0045] Preferably, in the aqueous zinc-iodine battery, the molar concentration of the zinc salt is 0.5-5 M, and the molar concentration of the iodine salt is 0.05-2 M.

[0046] The present application also provides the use of the organic cathode material described in the first aspect in an aqueous zinc-ion battery. Specifically, it is used as a cathode material for the battery. The aqueous zinc-ion battery at this time can be a zinc-naphthoquinone battery or a zinc-iodine battery.

[0047] The present application has the following beneficial effects:

[0048] 1. The present application provides a cathode material based on aromatic organic compounds. By using carbon powder particles to uniformly mix naphthoquinone, methylnaphthoquinone, and 2-hydroxy-1,4-naphthoquinone organic compounds as the organic cathode respectively, excellent electrochemical performance is shown in an aqueous zinc-organic battery matched with a zinc salt electrolyte and a zinc metal anode.

[0049] 2. Preferably, by using functionalized carbon powder, such as negatively charged porous activated carbon (PC) particles, to uniformly mix naphthoquinone, methylnaphthoquinone, and 2-hydroxy-1,4-naphthoquinone organic compounds as the organic cathode respectively, excellent electrochemical performance is shown in an aqueous zinc-organic battery matched with a zinc salt electrolyte and a zinc metal anode.

[0050] 3. In the preferred technical solution, by introducing phenolic hydroxyl (-OH) or methyl (-CH 3 ) groups, the organic structure of naphthoquinone is reasonably designed to achieve highly reversible proton insertion / extraction of chemical properties. Introducing hydroxyl and methyl groups will significantly change the electron distribution, solubility, chemical reactivity, and biological activity of the organic molecule naphthoquinone. Therefore, after introducing the groups, the reaction activity can be enhanced. Among them, the methyl group can increase the hydrophobicity of the molecule, reduce the solubility in water, avoid the dissolution of the cathode material in the electrolyte, and is beneficial to improving the cycle stability of the battery. The hydroxyl group can provide reaction sites and is easy to participate in reactions such as oxidation and esterification. The methyl group may affect the progress of certain reactions through steric hindrance effects.

[0051] 4. Different from the previously reported organic / conductive carbon mixed electrodes, the present application constructs a modified organic cathode / electrolyte interface (CEI) layer through functionalized carbon powder, such as negatively charged porous PC, to "capture" and promote proton insertion into the organic host, thus solving the slow kinetic problems caused by zinc ion desolvation and high charge interface transport energy barriers. Due to the "proton confinement" effect of negatively charged porous carbon, the methylnaphthoquinone cathode based on proton deintercalation reaction shows high capacity and excellent cycle stability.

[0052] 5. Particularly, in the aqueous zinc-ion battery, methylnaphthoquinone contains a hydrophobic methyl group (-CH 3) can significantly improve its dissolution resistance in aqueous electrolytes, thereby achieving an ultra-stable menadione cathode.

[0053] 6. This application shows excellent electrochemical performance in aqueous zinc-iodine batteries by using functionalized carbon powder, such as negatively charged porous activated carbon (PC) particles, uniformly mixed with naphthoquinone-type organic matter as organic positive electrode materials, and matching with zinc salt electrolyte containing a certain concentration of iodine ions and zinc metal negative electrode. Taking the menadione molecule with the best battery performance as an example, the carbonyl group of menadione can not only effectively promote the insertion and extraction of protons, but also effectively anchor polyiodide ions to inhibit the shuttling of polyiodide ions, catalyze the conversion of iodine, and reduce the growth of zinc dendrites, thereby constructing an aqueous zinc-iodine battery with high energy density and long life.

[0054] 5. The material of this application can improve the specific capacity and cycle stability of aqueous zinc batteries. Specifically: Figure 7 It can be seen that at a current density of 1Ag -1 Under the condition of , after nearly 5000 charge and discharge cycles, its capacity retention rate can still be as high as 99%, and the specific capacity of the positive electrode material of Example 1 (menadione in the figure) is still as high as nearly 240mAh g -1 , showing high specific capacity and excellent cycle stability. Figure 9 It can be seen that the positive electrode material of Example 1 has a high -1 The average discharge capacities were 273, 262, 255, 241, 235, 220 and 205 mAh g -1 The overall output capacity is high and the performance is relatively stable when the current density changes. Compared with the other two organics, its rate performance advantage is very obvious. Figure 10 It can be seen that at 10.0Ag -1 Under the high current density, the positive electrode material of Example 1 still shows amazing long cycle stability. After up to 10,000 charge and discharge cycle tests, its capacity retention rate can still be as high as 94%, the battery can still maintain excellent stability, and its specific capacity can also be maintained at a good level, indicating that the negatively charged porous activated carbon composite menadione cathode, with its unique "proton restriction" and special proton insertion ability, is used in aqueous zinc batteries to obtain fast charging capability, strong stability and high capacity.

[0055] 6. The material of the present application can improve the specific capacity and cycle stability of aqueous zinc-iodine batteries. Specifically, it is manifested as follows: Figure 13 It can be seen that at a current density of 0.5Ag -1Under the condition of [conditions not specified], after nearly 800 charge-discharge cycles, its capacity retention rate can still be as high as 97.6%. The specific capacity of the cathode material in Example 2 (naphthoquinone as the legend) is still as high as nearly 410 mAh g -1 , showing high specific capacity and extremely excellent cycle stability. Figure 14 It can be seen that: the average discharge capacities of the cathode material of Example 1 at 0.5, 1.0, 2.0, 3.0, 5.0, 7.0 and 10.0 A-g -1 are 410, 389, 350, 335, 324, 311 and 300 mAh g respectively -1 . Overall, it shows high-capacity output and maintains relatively stable performance when the current density changes. Compared with the other two organic substances, its rate performance advantage is very obvious. From Figure 15 it can be known that at a large current density of 30.0 A-g -1 , the cathode material of Example 2 still shows amazing long cycle stability. After undergoing up to 50,000 charge-discharge cycle tests, its capacity retention rate can still be as high as 83.5%. The battery can still maintain excellent stability, and its specific capacity can also be maintained at a good level. This shows that the cathode material can effectively anchor polyiodide ions, inhibit their shuttle, thereby reducing the corrosion of the zinc negative electrode, reflecting its excellent performance under long cycle life. Brief Description of the Drawings

[0056] Figure 1 is a scanning electron microscope image of the cathode material provided in Example 1 of this application;

[0057] Figure 2 is a transmission electron microscope image of the cathode material provided in Example 1 of this application;

[0058] Figure 3 is the BET data of the functionalized porous activated carbon provided in Example 1 of this application;

[0059] Figure 4 is the FTIR graph of the activated carbon provided in Example 1 of this application;

[0060] Figure 5 is the FTIR graph of the cathode material provided in Example 1 of this application;

[0061] Figure 6 is the in-situ pH graph of the cathode material provided in Example 1 of this application;

[0062] Figure 7 The cathode material provided in Example 1 of this application is used as the cathode of an aqueous zinc battery at a current density of 100 amperes per gram (abbreviated as @0.1 A-g -1Charge-discharge long cycle diagram under

[0063] Figure 8 The electrochemical rate performance diagrams of the cathode materials provided in Example 1 and Comparative Example 1 of this application as the cathodes of aqueous zinc batteries, with current densities of 0.1, 0.2, 0.5, 1.0, 2.0, 5.0, and 10.0 A g -1 ;

[0064] Figure 9 The charge-discharge curve diagrams of the cathode material provided in Example 1 of this application as the cathode of an aqueous zinc battery, with the current densities for constant current charge-discharge being 0.05, 0.1, 0.2, 0.5, 1.0, 2.0, 5.0, 7.0, 10.0, 20.0, and 30.0 A g -1 ;

[0065] Figure 10 The charge-discharge long cycle comparison diagrams of the cathode material provided in Example 1 of this application as the cathode of an aqueous zinc battery at current densities of 1000, 10000, and 30000 mA g (abbreviated as @10 A g -1 );

[0066] Figure 11 The element distribution diagram of the cathode material provided in Example 2 of this application;

[0067] Figure 12 The FTIR diagram of the cathode material provided in Example 2 of this application;

[0068] Figure 13 The charge-discharge long cycle diagram of the cathode material provided in Example 1 of this application as the cathode of an aqueous zinc battery at a current density of 500 A g (abbreviated as @0.5 A g -1 )(the left arrow corresponds to the specific capacity at different cycle numbers, and the right arrow corresponds to the Coulombic efficiency at different cycle numbers);

[0069] Figure 14 The electrochemical rate performance diagrams of the cathode materials provided in Example 2 and Comparative Example 1 of this application as the cathodes of aqueous zinc batteries, with current densities of 0.5, 1.0, 2.0, 3.0, 5.0, 7.0, and 10.0 A g -1 ;

[0070] Figure 15 The charge-discharge long cycle comparison of the cathode materials provided in Example 2 and Comparative Example 1 of this application as the cathodes of aqueous zinc-iodine batteries at a current density of 30000 mA g (abbreviated as @30.0 A g -1 );

[0071] Figure 16 The positive electrode materials of Example 1 were used as the positive electrodes of aqueous zinc-ion batteries at a current density of 0.1 A / g (abbreviated as @0.1 Ag -1 ) for the charge-discharge long cycle comparison chart;

[0072] Figure 17 The positive electrode materials of Example 1 were used as the positive electrodes of aqueous zinc-ion batteries at a current density of 0.1 A / g (abbreviated as @0.1 Ag -1 ) for the charge-discharge long cycle comparison chart;

[0073] Figure 18 The positive electrode materials of Example 1 were used as the positive electrodes of aqueous zinc-iodine batteries at a current density of 0.1 A / g (abbreviated as @0.1 Ag -1 ) for the charge-discharge long cycle comparison chart. Detailed implementation manners

[0074] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the protection scope of the present application.

[0075] Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in the present application can be obtained through market purchases or can be prepared by existing methods. The experimental methods without specific conditions noted in the following embodiments are usually determined according to national standards. If there is no corresponding national standard, they are carried out according to general international standards, conventional conditions, or the conditions recommended by the manufacturer.

[0076] Menadione, activated carbon, and super p used in the examples and comparative examples were obtained by purchase.

[0077] Example 1

[0078] A method for preparing a positive electrode material, the method comprising:

[0079] S1. Add a certain amount of commercial activated carbon material to a certain amount of 2.0 mol / l nitric acid to obtain solution A, and the mass-volume ratio of the activated carbon material to nitric acid is 1 g:5 L. Place solution A in a sealed Teflon-lined stainless steel autoclave and perform hydrothermal treatment at 140 °C for 12 hours to obtain solution B. Centrifuge the acid-treated solution B and wash it several times alternately with deionized water and ethanol until the pH value is close to about 7. After freeze-drying, functionalized porous activated carbon is obtained.

[0080] S2. Physically grind menadione, functionalized porous activated carbon, super P, and binder (PVDF) in a mass ratio of 5:3.5:0.5:1, and then uniformly mix them into an N-methylpyrrolidone solution to obtain a slurry;

[0081] S3. Uniformly coat the obtained slurry on carbon cloth with a loading amount of 1.5 mg to 2.0 mg, and dry it at 60 °C for 24 hours to obtain the modified positive electrode material.

[0082] The aqueous zinc battery of this embodiment is composed of a positive electrode, a negative electrode, a separator, and an electrolyte. The negative electrode uses a commercial high-purity zinc sheet with a thickness of 0.1 mm. The electrolyte is an aqueous solution of zinc sulfate heptahydrate, where the concentration of zinc sulfate heptahydrate is 2 mol / L, and the separator uses a glass fiber material. During assembly, the prepared positive electrode sheet, negative electrode sheet, glass fiber separator, and electrolyte are combined into an aqueous zinc ion secondary battery. During the assembly process, the separator is located between the positive electrode and the negative electrode, presenting a sandwich-like stacked structure, namely the positive electrode, the separator, and the negative electrode in sequence.

[0083] Example 2

[0084] A preparation method of a positive electrode material, the method comprising:

[0085] S1. Add a certain amount of commercial activated carbon material to a certain amount of 5.0 mol / l nitric acid to obtain solution A, and the mass-volume ratio of the activated carbon material to nitric acid is 1 g:5 L. Place solution A in a sealed Teflon-lined stainless steel autoclave and perform hydrothermal treatment at 140 °C for 6 hours to obtain solution B. Centrifuge the acid-treated solution B and wash it several times alternately with deionized water and ethanol until the pH value is close to about 7. After freeze-drying, functionalized porous activated carbon is obtained.

[0086] S2. Physically grind menadione, functionalized porous activated carbon, super P, and binder (PVDF) in a mass ratio of 5:3.5:0.5:1, and then uniformly mix them into an N-methylpyrrolidone solution to obtain a slurry;

[0087] S3. Uniformly coat the obtained slurry on carbon cloth with a loading amount of 1.5 mg to 2.0 mg, and dry it at 60 °C for 24 hours to obtain the modified positive electrode material.

[0088] The aqueous zinc-iodine battery of this embodiment is composed of a positive electrode, a negative electrode, a separator, and an electrolyte. The negative electrode uses a commercial high-purity zinc sheet with a thickness of 0.1 mm. The electrolyte is an aqueous solution of zinc trifluoromethanesulfonate and ammonium iodide. The concentration of zinc trifluoromethanesulfonate is 2 mol / L, and the concentration of ammonium iodide is 0.3 mol / L. The separator uses a glass fiber material. During assembly, the prepared positive electrode sheet, negative electrode sheet, glass fiber separator, and electrolyte are combined into an aqueous zinc-iodine secondary battery. During the assembly process, the separator is located between the positive electrode and the negative electrode, presenting a sandwich-like stacked structure, which is the positive electrode, the separator, and the negative electrode in sequence.

[0089] Example 3

[0090] S1. Add a certain amount of commercial activated carbon material to a certain amount of 2.0 mol / l nitric acid to obtain solution A. The mass-volume ratio of the activated carbon material to nitric acid is 1 g:5 L. Place solution A in a sealed Teflon-lined stainless steel autoclave and perform hydrothermal treatment at 150 °C for 12 hours to obtain solution B. Centrifuge the acid-treated solution B and wash it several times alternately with deionized water and ethanol until the pH value is close to about 7. After freeze-drying, functionalized porous activated carbon is obtained.

[0091] S2. Physically grind menadione, functionalized porous activated carbon, super P, and binder (PVDF) in a mass ratio of 5:2:2:1, and then uniformly mix them into an N-methylpyrrolidone solution to obtain a slurry;

[0092] S3. Uniformly coat the obtained slurry on carbon cloth with a loading amount of 1.5 mg to 2.0 mg, and dry it at 60 °C for 24 hours to obtain the modified positive electrode material.

[0093] The aqueous zinc battery of this embodiment is composed of a positive electrode, a negative electrode, a separator, and an electrolyte. The negative electrode uses a commercial high-purity zinc sheet with a thickness of 0.1 mm. The electrolyte is an aqueous solution of zinc trifluoromethanesulfonate, where the concentration of zinc trifluoromethanesulfonate is 2 mol / L. The separator uses a glass fiber material. During assembly, the prepared positive electrode sheet, negative electrode sheet, glass fiber separator, and electrolyte are combined into an aqueous zinc-ion secondary battery. During the assembly process, the separator is located between the positive electrode and the negative electrode, presenting a sandwich-like stacked structure, which is the positive electrode, the separator, and the negative electrode in sequence.

[0094] Example 4

[0095] S1. Add a certain amount of commercial activated carbon material to a certain amount of 3.0 mol / l nitric acid to obtain solution A, with the mass-volume ratio of the activated carbon material to nitric acid being 1 g:8 L. Place solution A in a sealed Teflon-lined stainless steel autoclave and conduct hydrothermal treatment at 180 °C for 6 hours to obtain solution B. Centrifuge the acid-treated solution B and wash it several times alternately with deionized water and ethanol until the pH value approaches approximately 7. After freeze-drying, functionalized porous activated carbon is obtained.

[0096] S2. Physically grind menadione, functionalized porous activated carbon, super P, and binder (PVDF) in a mass ratio of 5:2:2:1, and then uniformly mix them into an N-methylpyrrolidone solution to obtain a slurry.

[0097] S3. Uniformly coat the obtained slurry on carbon cloth with a loading amount of 1.5 mg - 2.0 mg, and dry it at 60 °C for 24 hours to obtain the modified positive electrode material.

[0098] The aqueous zinc-iodine battery of this example consists of a positive electrode, a negative electrode, a separator, and an electrolyte. The negative electrode uses a commercial high-purity zinc sheet with a thickness of 0.1 mm, and the electrolyte is an aqueous solution mixture of zinc trifluoromethanesulfonate and potassium iodide. The concentration of zinc trifluoromethanesulfonate is 2 mol / L, and the concentration of potassium iodide is 0.3 mol / L. The separator uses a glass fiber material. During assembly, the prepared positive electrode sheet, negative electrode sheet, glass fiber separator, and electrolyte are combined into an aqueous zinc-iodine secondary battery. During the assembly process, the separator is located between the positive electrode and the negative electrode, presenting a sandwich-like stacked structure, which is the positive electrode, separator, and negative electrode in sequence.

[0099] Example 5

[0100] S1. Add a certain amount of commercial activated carbon material to a certain amount of 5.0 mol / l nitric acid to obtain solution A, with the mass-volume ratio of the activated carbon material to nitric acid being 1 g:10 L. Place solution A in a sealed Teflon-lined stainless steel autoclave and conduct hydrothermal treatment at 140 °C for 6 hours to obtain solution B. Centrifuge the acid-treated solution B and wash it several times alternately with deionized water and ethanol until the pH value approaches approximately 7. After freeze-drying, functionalized porous activated carbon is obtained.

[0101] S2. Physically grind naphthoquinone, functionalized porous activated carbon, super P, and binder (PVDF) in a mass ratio of 5:3.5:0.5:1, and then uniformly mix them into an N-methylpyrrolidone solution.

[0102] S3. Uniformly coat the obtained slurry on carbon cloth with a loading amount of 1.5 mg - 2.0 mg, and dry it at 60 °C for 24 hours to obtain the modified positive electrode material.

[0103] The aqueous zinc battery of this embodiment consists of a positive electrode, a negative electrode, a separator, and an electrolyte. The negative electrode uses a commercial high-purity zinc sheet with a thickness of 0.1 mm. The electrolyte is an aqueous solution of zinc sulfate heptahydrate, in which the concentration of zinc sulfate heptahydrate is 2 mol / L, and the separator uses a glass fiber material. During assembly, the prepared positive electrode sheet, negative electrode sheet, glass fiber separator, and electrolyte are combined into an aqueous zinc-iodine secondary battery. During the assembly process, the separator is located between the positive electrode and the negative electrode, presenting a sandwich-like stacked structure, namely the positive electrode, the separator, and the negative electrode in sequence.

[0104] Example 6

[0105] S1. Add a certain amount of commercial activated carbon material to a certain amount of 5.0 mol / l nitric acid to obtain solution A. Place solution A in a sealed Teflon-lined stainless steel autoclave and perform hydrothermal treatment at 140 °C for 6 hours to obtain solution B. Centrifuge the acid-treated solution B and wash it several times alternately with deionized water and ethanol until the pH value is close to about 7. After freeze-drying, functionalized porous activated carbon is obtained.

[0106] S2. Physically grind 2-hydroxy-1,4-naphthoquinone, functionalized porous activated carbon, super P, and binder (PVDF) in a mass ratio of 5:3.5:0.5:1, and then uniformly mix them into an N-methylpyrrolidone solution to obtain a slurry;

[0107] S3. Uniformly coat the obtained slurry on carbon cloth with a loading amount of 1.5 mg to 2.0 mg, and dry it at 60 °C for 24 hours to obtain the modified positive electrode material.

[0108] The aqueous zinc battery of this embodiment consists of a positive electrode, a negative electrode, a separator, and an electrolyte. The negative electrode uses a commercial high-purity zinc sheet with a thickness of 0.1 mm. The electrolyte is an aqueous solution of zinc sulfate heptahydrate, in which the concentration of zinc sulfate heptahydrate is 2 mol / L, and the separator uses a glass fiber material. During assembly, the prepared positive electrode sheet, negative electrode sheet, glass fiber separator, and electrolyte are combined into an aqueous zinc-ion secondary battery. During the assembly process, the separator is located between the positive electrode and the negative electrode, presenting a sandwich-like stacked structure, namely the positive electrode, the separator, and the negative electrode in sequence.

[0109] Comparative Example 1

[0110] S1. Physically grind commercial activated carbon, super p, and binder (PVDF) in a mass ratio of 8.5:0.5:1, and then uniformly mix them into an N-methylpyrrolidone solution to obtain a slurry;

[0111] S3. Uniformly coat the obtained slurry on carbon cloth with a loading amount of 1.5 mg to 2.0 mg, and dry it at 60 °C for 24 hours to obtain the modified positive electrode material.

[0112] The aqueous zinc-iodine battery of this embodiment consists of a positive electrode, a negative electrode, a separator, and an electrolyte. The negative electrode uses a commercial high-purity zinc sheet with a thickness of 0.1 mm. The electrolyte is an aqueous solution of zinc trifluoromethanesulfonate and ammonium iodide. The concentration of zinc trifluoromethanesulfonate is 2 mol / L, and the concentration of ammonium iodide is 0.3 mol / L. The separator uses a glass fiber material. During assembly, the prepared positive electrode sheet, negative electrode sheet, glass fiber separator, and electrolyte are combined into an aqueous zinc-iodine secondary battery. During the assembly process, the separator is located between the positive electrode and the negative electrode, presenting a sandwich-like stacked structure, namely the positive electrode, the separator, and the negative electrode in sequence.

[0113] Material characterization and performance testing:

[0114] Figure 1 Scanning electron microscope image of the positive electrode material provided for Example 1. The figure shows that the presented particles exhibit diverse shapes and sizes, and it can be seen that smaller particles are combined with larger flake structures. This mixed morphology makes the surface characteristics of the composite material more complex. The material surface shows obvious roughness, which generally reflects the porous characteristics of activated carbon. The porosity of activated carbon helps to increase the specific surface area of the material, thereby optimizing its performance in electrochemical reactions.

[0115] Figure 2 Transmission electron microscope image of the positive electrode material of the aqueous zinc battery provided for Example 1. In this image, an irregular particle shape is presented with a distinct contour and a clear boundary from the surrounding environment. The size of the particle is in the range of 200 nanometers, indicating its characteristics at the nanoscale. From the thickness and transparency of the particle, the microscopic structural details inside the composite material are shown. There may be multiple small holes and irregular cracks, and these features usually indicate its porosity, which is crucial for electrochemical performance.

[0116] Figure 3 BET data of the functionalized activated carbon. As the relative pressure increases, the adsorption amount gradually rises and tends to be stable. Eventually, the adsorption amount reaches about 700 cm 3 g -1 , and the BET surface area is marked as 2323.9 m 2 g -1 in the figure, which indicates that the material has a high specific surface area. The pore size distribution diagram shows the size and distribution of pore sizes in the material. It can be seen that most of the pore sizes are concentrated in a relatively small range, and there is an obvious change at a pore size of about 2.11 nm, indicating that PC acidified with concentrated nitric acid shows a high specific surface area (2323.9 m 2 g -1 ) and functional groups (-OH and -COOH) to achieve better binding of PC with organic substances.

[0117] Figure 4 are the infrared spectra of activated carbon before and after acidification. The initial activated carbon has an absorption peak at approximately 1650 cm -1 . This peak corresponds to the vibration of the carbon-carbon double bond (C═C). The changes in the peak intensity and position of the functionalized activated carbon imply changes in the surface chemical environment of the activated carbon. The C═O stretching vibration peak at shorter wavelengths is more prominent, and the functionalized material shows more distinct characteristics of carboxyl (-COOH) or hydroxyl (-OH). After functionalization, the intensity of C-O increases, and hydroxyl (-OH) or other oxygen-containing functional groups are introduced onto the surface of the activated carbon. This indicates that more carboxyl or hydroxyl functional groups are introduced through acidification treatment, which improves the hydrophilicity and reactivity of the activated carbon. By comparing the infrared spectra, the acidification treatment significantly changes the surface chemical structure of the activated carbon, making it more functional and contributing to the improvement of its performance and stability in various applications such as batteries, electrochemical sensors, etc.

[0118] Figure 5 are the infrared spectra of three organic compounds (Lawson (2-hydroxy-1,4-naphthoquinone), Menadione (menadione), and NQ (naphthoquinone)). This figure shows the infrared spectra (FTIR) of the three organic compounds (Lawson, Menadione, and NQ), covering the wavenumber range from 4000 cm -1 to 1000 cm -1 . All three organic compounds show the characteristics of O-H and C-H, demonstrating that they contain oxygen-containing functional groups and hydrocarbon structures. Lawson (2-hydroxy-1,4-naphthoquinone) and Menadione (menadione) are more prominent in the absorption of hydroxyl and carbonyl groups, which may be related to their biological activity and chemical reactivity. NQ (naphthoquinone) shows stronger aromatic absorption, indicating its stability and unique aromatic properties, which may endow it with different functional characteristics in chemical applications.

[0119] Figure 6 is the change in pH in the electrolyte during charge and discharge. Arrows in the figure indicate the directions of discharge and charge, showing the voltage changes of the battery during discharge and charge at different capacities. When the charge accumulates to a certain value, the position marked "hydrogen ion insertion" is shown. This indicates that during the discharge process, the hydrogen ion insertion process corresponds to the increase in battery capacity. During the charge and discharge processes, the pH value changes with charge and discharge, which also corresponds to the chemical reactions in the battery.

[0120] Using the same concentration of zinc salt, the positive electrode materials provided in the examples and comparative examples are used to construct an aqueous zinc battery. Specifically, the positive electrode material of Example 1 is used as the positive electrode, zinc foil is used as the negative electrode, and the electrolyte is 2M ZnSO 4 ·7H 2O, charge-discharge tests and long charge-discharge cycle tests were carried out on the battery, and the results are as Figures 7 to 15 shown.

[0121] Figure 7 are the long charge-discharge cycle conditions of the cathode materials provided in Example 1 and Examples 5 and 6 as the cathode of a zinc-ion battery at a current density of 0.1 A g -1 . It can be seen from Figure 7 that under the condition of a current density of 0.1 A g -1 , after nearly 100 charge-discharge cycles, the specific capacities of the cathode materials of Examples 1, 5, and 6 reached 270 mAh g -1 , 180 mAh g -1 , and 182 mAh g -1 respectively, showing extremely excellent cycle stability.

[0122] Charge-discharge tests were carried out on the cathode material of Example 1. Figure 8 are the rate performance of the cathode materials provided in Examples 1, 5, and 6 at different current densities and Figure 9 the corresponding charge-discharge curves of Example 1. The current densities used for constant current charge-discharge were 0.05, 0.1, 0.2, 0.5, 1.0, 2.0, 5.0, 7.0, 10.0, 20.0, and 30.0 A g -1 . The average discharge capacities of the cathode materials of Examples 1, 5, and 6 (the legends are menadione, naphthoquinone, 2-hydroxy-1,4-naphthoquinone) at 0.1, 0.2, 0.5, 1.0, 2.0, 5.0, and 10.0 A g -1 are 270 (180, 250), 260 (180, 160), 250 (140, 140), 240 (130, 120), 230 (110, 80), 220 (90, 50), and 200 (80, 10) mAh g -1 respectively. Overall, it shows an excellent trend of high-capacity output and relatively stable change with the current density. Compared with the cathode materials of Examples 5 and 6 (the legends are naphthoquinone, 2-hydroxy-1,4-naphthoquinone), the rate performance of Example 1 is significantly superior. It shows that the optimal battery performance is obtained by compounding menadione with functionalized activated carbon.

[0123] Figure 10 It shows that menadione has a specific capacity of 250 mAh g -1 at a current density of 1 A g -1 , 10 A g -1 , and 30 A g -1 , 200 mAh g -1 , and 105 mAh g -1, the cathode material of Example 1 still exhibited amazing long-cycle stability. After undergoing up to 20,000 charge-discharge cycles, its capacity retention rate was still as high as 94.8%. The battery could still maintain excellent stability, and its specific capacity could also be maintained at a good level. This fully demonstrated the excellent performance of this cathode material under high-current conditions and also indicated the crucial importance of functionalized activated carbon for menadione. The negatively charged porous PC "captured" and promoted proton insertion into the organic host by constructing a modified cathode / electrolyte interface layer, thus solving the slow kinetics problems caused by ion desolvation and transport across the CEI layer. Due to the "proton limitation" effect, the menadione cathode composite with negatively charged porous carbon showed high capacity and long cycles.

[0124] Figure 11 Scanning electron microscope (SEM) images and elemental mapping diagrams of the cathode material of Example 2. The surface morphology of the composite material can be observed in the figure. The surface presents an irregular granular structure, indicating good interaction between menadione and activated carbon. The magnified image (inset) in the lower left corner shows more detailed structural features, indicating the porosity and roughness of the material, which helps to increase the contact area with the electrolyte and thus improve the electrochemical performance. The C elemental mapping diagram on the right shows that the distribution of carbon in the composite material is very uniform, indicating that the composition of activated carbon is well retained and distributed in the composite. This is consistent with the granular structure in the SEM image. The O elemental mapping diagram shows the distribution of oxygen in the material. Although the distribution of oxygen seems relatively sparse, it still exists in the composite material, indicating that the introduction of menadione has successfully introduced oxygen-containing functional groups, which may have a positive impact on the electrochemical properties of the material.

[0125] Figure 12 Infrared spectra of menadione and functionalized activated carbon. This figure shows the comparison of the infrared spectra of menadione and functionalized activated carbon (AC), and the specific analysis is as follows: The O-H stretching vibration absorption peak indicates the presence of the hydroxyl (-OH) functional group in menadione. The intensity of this peak indicates the relatively high hydrophilicity of menadione. The C-H absorption peak is mainly due to the presence of methyl (-CH 3 ) and methylene (-CH 2 ) in menadione. Strong absorption peaks can also be seen for the C=C and C=O absorption peaks, which reflect the presence of the characteristic double bonds and carbonyl groups in its molecular structure, indicating the presence of the carboxyl (-COOH) functional group in menadione. The entire infrared spectrum of activated carbon is relatively flat, indicating that its functional groups and structure are relatively simple. The stronger absorption peaks are mainly concentrated in the 1650 - 1700 cm -1 region, in contrast to the more complex menadione.

[0126] Long charge-discharge cycle tests were carried out on the cathode material provided in Example 2.Figure 13 The positive electrode materials provided in Example 2 and Comparative Example 1 were used as the positive electrode of an aqueous zinc-iodine battery, and the charge-discharge long cycle conditions were tested at a current density of 0.5 Ag -1 . As can be seen from Figure 13 , under the condition of a current density of 0.5 Ag -1 , after more than 800 charge-discharge cycles, the specific capacity of the positive electrode material of Example 2 reached 430 mAh g -1 , showing extremely excellent cycle stability.

[0127] The charge-discharge test was carried out on the positive electrode material provided in Example 2. Figure 14 The rate performance of the positive electrode materials of Example 2 (Menadione) and Comparative Example 1 (AC) as the positive electrode of an aqueous zinc-iodine battery at different current densities is shown. The current densities used for constant current charge-discharge were 0.5, 1.0, 2.0, 3.0, 5.0, 7.0, and 10.0 Ag -1 respectively. The average discharge capacities of the positive electrode material of Example 2 (the legend is menadione) were 410, 389, 350, 335, 324, 311, and 300 mAh g -1 respectively. Overall, it shows an excellent trend of high-capacity output and relatively stable change with the current density. Compared with the positive electrode material of Comparative Example 1 (the legend is AC), which is an unmodified similar material, its rate performance advantage is significant.

[0128] Figure 15 The charge-discharge long cycle comparison of the positive electrode materials of Example 2 (Menadione) and Comparative Example 1 (AC) of the present application as the positive electrode of an aqueous zinc-iodine battery at a current density of 30,000 mA per gram (abbreviated as @30.0 A g -1 ) is shown. Figure 15 It shows that under the condition of a current density of 30 Ag -1 , its specific capacity reached 220 mAh g -1 . The positive electrode material of Example 2 still showed amazing long cycle stability. After undergoing up to 50,000 charge-discharge cycle tests, its capacity retention rate was still as high as 83.5%, and the battery could still maintain excellent stability. This shows that the positive electrode material can effectively anchor polyiodide ions, inhibit their shuttling, thereby reducing the corrosion of the zinc negative electrode, reflecting its excellent performance under long cycle life.

[0129] The selection of the carbon powder for the positive electrode material of Example 7,

[0130] Mix menadione, different types of carbon powders (graphene, functionalized activated carbon, carbon nanotubes), super p, and binder in a mass ratio of 5:3.5:0.5:1, and prepare the material as the battery positive electrode in the manner of Example 1. The electrolyte is 2M trifluoromethanesulfonic acid. Figure 16 The charge-discharge long cycle comparison diagrams of the positive electrode materials as the positive electrodes of zinc-ion batteries at a current density of 0.1 A per gram (abbreviated as @0.1Ag -1 ). Figure 16 It can be seen that for the positive electrode materials obtained by uniformly compounding menadione with functionalized activated carbon, graphene, and carbon nanotubes respectively, their specific capacities are 270 mAh g -1 , 50 mAh g -1 , 30 mAh g -1 respectively. This indicates that among the three carbon materials, functionalized activated carbon is preferentially selected as the carbon powder in the positive electrode material.

[0131] Selection of the positive electrode material ratio in Example 8

[0132] Mix menadione, functionalized activated carbon, super p, and binder in mass ratios of 4.5:5:0.5:1, 5:3.5:0.5:1, 6.5:2:0.5:1, and 8:0.5:0.5:1 respectively, and prepare the material as the battery positive electrode in the manner of Example 1. Figure 17 The charge-discharge long cycle comparison diagrams of the positive electrode materials as the positive electrodes of zinc-ion batteries at a current density of 1 A per gram (abbreviated as @1Ag -1 ). Figure 17 It can be seen that the specific capacities of the positive electrode materials with the four ratios are 270 mAh g -1 (5:3.5:0.5:1), 220 mAh g -1 (6.5:2:0.5:1), 165 mAh g -1 (4.5:5:0.5:1), 125 mAh g -1 (8:0.5:0.5:1) respectively. This indicates that menadione, functionalized activated carbon, super p, and binder with a mass ratio of 5:3.5:0.5:1 are preferentially selected as the positive electrode material.

[0133] Selection of the electrolyte concentration in Example 9

[0134] Mix menadione, functionalized activated carbon, super p and binder in a mass ratio of 5:3.5:0.5:1 and prepare the material in the manner of Example 1 as the positive electrode of the battery. The electrolytes are 2M zinc trifluoromethanesulfonate and ammonium iodide with different concentrations (0.2M, 0.3M, 0.5M) respectively. Figure 18 As the positive electrode materials, they are used as the positive electrodes of aqueous zinc-iodine batteries at a current density of 3 A per gram (abbreviated as @3A g -1 ) for the charge-discharge long cycle comparison chart. Figure 17 It can be seen that different specific capacities are obtained with electrolytes of different concentrations of iodine salts in this application, which are 300 mAh g from low to high respectively -1 (0.2M), 360 mAh g -1 (0.3M), 420 mAh g -1 (0.5M). However, because the initial capacity of the high-concentration electrolyte is high, at the same time, the high-concentration iodine salt will cause the shuttle of polyiodide ions, reducing the cycle life of the battery; the low-concentration iodine salt cannot meet the capacity requirements of the battery system. Therefore, the concentration of iodine in the electrolyte is preferably 0.3M as the concentration of iodine in the system.

[0135] In summary, in the materials of this application, the inherent porosity and electronegative carbonyl group of the functionalized carbon powder help to enhance the reaction activity of the positive electrode material, build a "proton-rich" region around organic molecules, eliminate the slow charge transfer problem that has long existed at the positive electrode / electrolyte interface, promote the proton storage capacity while improving the cycle stability and reaction kinetics of the organic positive electrode material. At the same time, the carbonyl group contained in this organic positive electrode can not only effectively promote the insertion and extraction of protons, but also effectively catalyze the I - / I 0 transformation reaction and anchor polyiodide ions, inhibit the shuttle side reaction of polyiodide ions and reduce the growth of zinc dendrites, thereby significantly improving the specific capacity and cycle stability of aqueous zinc-iodine batteries. In addition, the functionalized porous carbon provides additional storage sites for protons and iodide ions for the organic positive electrode, further improving the specific capacity and rate performance of the naphthoquinone-based organic positive electrode, which is beneficial to the construction of a zinc-ion soft-pack battery based on a large-size high-loading organic positive electrode. Therefore, due to the synergistic confinement effect of "proton-iodide ion", the naphthoquinone-based organic positive electrode of this application, especially the menadione positive electrode, shows high specific capacity, excellent rate performance and ultra-long cycle life, providing key theoretical and technical support for advanced aqueous zinc-ion batteries.

Claims

1. An organic cathode material based on naphthoquinone, characterized in that: The positive electrode material includes: organic matter and carbon powder; The organic matter is one of naphthoquinone, menaquinone and 2-hydroxy-1,4-naphthoquinone; The carbon powder is selected from: one of graphene, activated carbon or carbon nanotubes. The carbon powder is functionalized carbon powder or non-functionalized carbon powder; The functionalized carbon powder is carboxylated carbon powder or hydroxylated carbon powder.

2. The naphthoquinone-based organic cathode material according to claim 1, characterized in that: The positive electrode material also contains a conductive agent and a binder, and the mass ratio of the organic matter, carbon powder, conductive agent and binder is (4-7):(4-1.5):(1-0.5):

1.

3. A method for preparing an organic cathode material based on naphthoquinone according to claim 1, characterized in that: The preparation method comprises the following steps: The positive electrode material precursor including organic matter and carbon powder is mixed, physically ground, and an organic solvent is added to obtain a slurry; The obtained slurry is coated on the current collector, and the positive electrode material is obtained after drying; The organic matter is one of naphthoquinone, menaquinone and 2-hydroxy-1,4-naphthoquinone; The carbon powder is selected from: one of graphene, activated carbon or carbon nanotubes; The carbon powder is functionalized carbon powder or non-functionalized carbon powder; The functionalized carbon powder is carboxylated carbon powder or hydroxylated carbon powder.

4. The preparation method according to claim 3, characterized in that: The positive electrode material precursor also includes: a conductive agent and a binder.

5. The preparation method according to claim 3, characterized in that: The preparation method of the functionalized carbon powder is as follows: Carbon powder is added to 2-5.0 mol / l nitric acid to obtain solution A, wherein the mass volume ratio of carbon powder to nitric acid is 1:5-1:

10. The solution A is placed in a sealed autoclave and subjected to hydrothermal treatment at 140-180° C. for 6-12 hours to obtain a solution B, and functionalized agglomerated carbon powder is obtained by solid-liquid separation.

6. The preparation method according to claim 4, characterized in that: The mass ratio of the organic matter, carbon powder, conductive agent and binder is (4-8):(5-0.5):(1-0.5):

1.

7. An aqueous zinc ion battery comprising the positive electrode material according to any one of claims 1 to 2.

8. The aqueous zinc ion battery according to claim 7, characterized in that: The molar concentration of the zinc salt in the electrolyte is 0.5-2M.

9. The aqueous zinc ion battery according to claim 7, characterized in that: The aqueous zinc ion battery is an aqueous zinc iodine battery.

10. Use of the organic cathode material according to claim 1 in aqueous zinc ion batteries.

Images