Nitrogen-doped zinc ion battery manganese-based positive electrode material and preparation method and application thereof

Abstract

The invention discloses a nitrogen-doped zinc ion battery manganese-based positive electrode material and a preparation method and application thereof, and the preparation method comprises the following steps: mixing a strong oxidant and a manganese salt, putting the mixture into a beaker, adding deionized water, and uniformly stirring to form a mixed solution; transferring the mixed solution into a high-pressure reaction kettle with a polytetrafluoroethylene lining, and heating the high-pressure reaction kettle in a drying oven; cooling, precipitating, filtering and washing for multiple times, and then putting into a drying oven for vacuum drying to obtain an original manganese-based positive electrode material; the preparation method comprises the following steps: respectively weighing an original manganese-based positive electrode material and hexamethylenetetramine, flatly laying the original manganese-based positive electrode material at the bottom of a lining of a reaction kettle, and putting the hexamethylenetetramine into a beaker; and putting the beaker into a reaction kettle, moving the beaker and the reaction kettle into a drying oven, and heating to obtain the surface nitrogen-doped manganese-based positive electrode material.

Description

Technical Field

[0001] The present invention relates to the technical field of zinc ion battery materials, and particularly to a nitrogen-doped manganese-based cathode material for zinc ion batteries, a preparation method thereof, and an application thereof. Background Art

[0002] In view of the continuous depletion of traditional fossil energy and the growing demand of modern people for flexible and wearable portable batteries, there is an urgent need to discover cleaner and more environmentally friendly energy storage devices. Although lithium-ion batteries dominate in the fields of electric vehicles, consumer electronics, and energy storage, their development is facing multiple dilemmas such as resource constraints, cost pressure, safety hazards, and performance bottlenecks.

[0003] Zinc ion batteries are a new type of secondary battery technology that has received much attention in recent years. Zinc is a metal element with abundant reserves in the earth's crust (about 100 times that of lithium), low price (about 1 / 3 of that of lithium), and less environmental impact during mining and processing. Compared with scarce resources such as lithium and cobalt relied on by lithium-ion batteries, zinc ion batteries are more sustainable. At the same time, zinc ion batteries have excellent theoretical capacity (819 mAh g -1 ), high energy density (5851 mAh cm -3 ), suitable redox potential, and mild aqueous electrolyte and other advantages, and have significant potential in large-scale energy storage (power grid peak shaving, renewable energy grid connection) and flexible electronics fields. With the demand for portable and bendable devices and the continuous in-depth research on gel-like electrolytes, flexible aqueous zinc-manganese-based batteries have gradually become a development trend. In short, as a new type of environmentally friendly energy storage component, aqueous zinc ion batteries have research potential to be explored.

[0004] However, the development of current zinc ion batteries still faces a series of challenges. For example, although layered manganese-based cathode materials (such as MnO2) in zinc ion batteries have advantages such as low cost, high theoretical capacity, and environmental friendliness, their practical applications are still restricted by multiple factors: First, during the charge and discharge process, the material is prone to crystal structure distortion or even collapse due to the Jahn-Teller distortion of Mn 3+ , and is accompanied by irreversible phase transformation (such as the transformation from layered structure to spinel), resulting in rapid capacity decay; second, the disproportionation reaction of Mn 3+ in the electrolyte will generate soluble Mn 2+ , which migrates to the zinc negative electrode to form an insulating by-product, exacerbating side reactions and efficiency decline. At the same time, the pH fluctuation of the electrolyte further accelerates manganese dissolution; in addition, Zn 2+ due to its double-charge characteristics and relatively large ionic radius There is a large resistance during interlayer diffusion, and the intrinsic electronic conductivity of the composite material is poor, which limits the rate performance; the repeated volume expansion (~10–20%) during the cycling process is also likely to cause particle pulverization and active material shedding, shortening the cycle life (usually <1000 cycles); while the relatively low working voltage (1.3–1.4V vs. Zn 2+ / Zn) also restricts the improvement of energy density. Therefore, developing more stable new cathode materials and suppressing the formation of side reaction products are the keys to the development of zinc-ion batteries. Selecting a suitable method to modify manganese-based cathode materials to improve their electrochemical performance is a research direction with practical significance.

[0005] Aiming at the problems of capacity decay, structural instability, and excessive deposition of by-products in manganese-based cathode materials, a large number of previous experimental studies and theoretical analyses show that the above problems are mainly due to the structural instability, excessive manganese dissolution, and excessive deposition of by-products in manganese-based cathode materials during charge and discharge. The structural instability makes the reversibility of manganese-based cathode materials poor, and the original structure collapses during charge and discharge, preventing the normal transmission of zinc ions and hydrogen ions. Excessive manganese dissolution reduces the amount of reactive substances, seriously hindering the battery capacity. The excessive deposition of by-products also hinders the effective transmission of various active substances in the electrolyte and the reversibility of the battery. Therefore, during charge and discharge, the overall degradation of the material structure seriously affects the performance stability of the electrode material. However, there is currently no relatively simple and effective treatment method to improve the above defects. Summary of the Invention

[0006] In response to the problems and requirements mentioned above, this solution proposes a nitrogen-doped manganese-based cathode material for zinc-ion batteries, its preparation method, and application. Due to the following technical features, it can achieve the above technical objectives and bring many other technical effects.

[0007] One objective of the present invention is to propose a nitrogen-doped manganese-based cathode material for zinc-ion batteries. The cathode material is a manganese-based compound doped with N ions on the surface. Among them, the manganese-based compound includes at least one of α-MnO2, β-MnO2, γ-MnO2, δ-MnO2, T-MnO2, λ-MnO2, Mn2O3, Mn3O4, and ZnMn2O4.

[0008] Another objective of the present invention is to propose a preparation method for a nitrogen-doped manganese-based cathode material for zinc-ion batteries, which includes the following steps:

[0009] S10: Mix a strong oxidant and a manganese salt in a beaker, add deionized water and stir evenly to form a mixed solution;

[0010] S20: Transfer the above mixed solution into a high-pressure reaction kettle with a polytetrafluoroethylene liner and place it in an oven for heating;

[0011] S30: After multiple cycles of cooling - precipitation - filtration - washing, it is placed in an oven for vacuum drying to obtain the original manganese - based cathode material;

[0012] S40: Weigh the original manganese - based cathode material and hexamethylenetetramine respectively. Spread the original manganese - based cathode material evenly on the bottom of the inner lining of the reaction kettle, and put the hexamethylenetetramine into a beaker;

[0013] S50: Put the beaker into the reaction kettle and transfer them together into the oven for heating to obtain the manganese - based cathode material with surface nitrogen doping.

[0014] In an example of the present invention, in the step S10, the strong oxidant and the manganese salt are added in a chemical molar ratio of 4:1 - 6:1.

[0015] In an example of the present invention, in the step S10, the strong oxidant is permanganate, persulfate or peroxide.

[0016] In an example of the present invention, the permanganate is AMnO4, where A is at least one of six metal ions of Li, Na, K, Ca, Mg, Zn; the persulfate is MS2O8, where M is at least one of three substances of NH4, Na, K; the peroxide is at least one of two substances of K2O2 and H2O2.

[0017] In an example of the present invention, in the step S10, the manganese salt is at least one of manganese sulfate, manganese acetate, manganese chloride, and manganese carbonate.

[0018] In an example of the present invention, in the step S30, after multiple cycles of cooling - precipitation - filtration - washing, it is placed in an oven at 80 - 110 °C for vacuum drying to obtain the original manganese - based cathode material.

[0019] In an example of the present invention, in the step S40, the mass ratio of the manganese - based oxide to hexamethylenetetramine is 1:0.015 - 0.05.

[0020] In an example of the present invention, in the step S50, the reaction kettle is transferred into the oven and heated at 180 - 200 °C to obtain the manganese - based cathode material.

[0021] Another object of the present invention is to propose an application of the cathode material prepared by the preparation method of the manganese - based cathode material for zinc - ion batteries as described above. The cathode material prepared by this preparation method is applied to the cathode material of zinc - ion batteries or power batteries.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The present invention uses a gas treatment method to treat the surface of the manganese-based cathode material. This method is easy to operate, simple and convenient. Compared with the traditional wet chemical method, the gas treatment method does not require the use of a large amount of solvents, so less waste liquid is generated and the impact on the environment is smaller. At the same time, the gas treatment method is easy to realize continuous and automated production and is suitable for large-scale industrial applications.

[0024] 2. The gas treatment with hexamethylenetetramine of the present invention also affects the charge-discharge reaction process of the manganese-based cathode material. It is found in experimental applications that nitrogen doping is successfully achieved on the surface of the manganese-based cathode material, and the dissolution of manganese is inhibited by bonding with the surface Mn (N-Mn bond), strengthening the structural stability of the manganese-based cathode material, reducing the internal impedance of the battery, and improving the capacity and rate performance of the zinc-ion battery.

[0025] The following will describe in more detail the optimal embodiments for implementing the present invention in conjunction with the accompanying drawings, so as to easily understand the features and advantages of the present invention. Brief Description of the Drawings

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments of the present invention will be briefly introduced below. Among them, the accompanying drawings are only used to show some embodiments of the present invention and do not limit all embodiments of the present invention thereto.

[0027] Figure 1 It is the XRD pattern of the powder of the δ-MnO2 cathode material before and after treatment according to Embodiment 1 of the present invention;

[0028] Figure 2 It is the XPS pattern of the powder of the δ-MnO2 cathode material before and after treatment according to Embodiment 1 of the present invention;

[0029] Figure 3 It is the EIS impedance pattern of the powder of the δ-MnO2 cathode material before and after treatment as the cathode at room temperature according to Embodiment 1 of the present invention;

[0030] Figure 4 It is the cyclic performance curve diagram of the powder of the δ-MnO2 cathode material before and after treatment as the cathode at room temperature when the current densities are 200, 500, 1000 and 2000 mA / g respectively according to Embodiment 1 of the present invention. Detailed Description of the Embodiments

[0031] In order to make the objectives, technical solutions, and advantages of the technical solutions of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of specific embodiments of the present invention. The same reference numerals in the drawings represent the same components. It should be noted that the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the described embodiments of the present invention without creative work fall within the scope of protection of the present invention.

[0032] Unless otherwise defined, the technical terms or scientific terms used herein shall have the ordinary meanings understood by those of ordinary skill in the art to which the present invention belongs. The "first", "second", and similar terms used in the specification and claims of this patent application for the present invention do not indicate any order, quantity, or importance, but are only used to distinguish different components. Similarly, terms such as "a" or "an" do not necessarily indicate a quantity limitation. The terms "comprising" or "including" and similar terms mean that the elements or objects appearing before this term cover the elements or objects listed after this term and their equivalents, without excluding other elements or objects. The terms "connected" or "coupled" and similar terms are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The terms "upper", "lower", "left", "right", etc. are only used to indicate relative positional relationships, and when the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0033] According to a nitrogen-doped zinc-ion battery manganese-based cathode material of the first aspect of the present invention, the cathode material is a manganese-based compound with N ions doped on the surface. Among them, the manganese-based compound includes at least one of α-MnO2, β-MnO2, γ-MnO2, δ-MnO2, T-MnO2, λ-MnO2, Mn2O3, Mn3O4, and ZnMn2O4.

[0034] The resources used for the manganese-based cathode material are rich and the cost is low. The crustal abundances of manganese (Mn) and zinc (Zn) are significantly higher than those of lithium (Li) and cobalt (Co), which are commonly used elements in the cathode materials of lithium-ion batteries: the reserves of manganese are about 500 times that of lithium, and the global distribution of zinc is also much wider than that of cobalt, greatly reducing the dependence on scarce resources. For example, the price of manganese-based materials such as manganese dioxide (MnO2) is only about 1 / 5 of that of lithium cobaltate (LiCoO2), and there is no need to rely on high-cost precious metals, making it economically viable for large-scale applications.

[0035] The zinc-ion battery using the manganese-based cathode material adopts an aqueous electrolyte, completely avoiding the risk of flammability and explosion of the organic electrolyte of the lithium-ion battery, and having no hidden danger of thermal runaway under conditions of puncture or overcharge, with higher safety.

[0036] The compounds of manganese and zinc in the manganese-based cathode material have much lower toxicity than the lithium-ion battery materials containing cobalt and nickel, and the aqueous system has no organic solvent pollution, and the recycling process is simpler. In addition, the carbon emissions throughout the life cycle from mining to production are reduced by about 30% compared with lithium-ion batteries, meeting the requirements of sustainable development.

[0037] The structural stability of the manganese-based cathode material is strengthened, reducing the internal impedance of the battery and improving the capacity and rate performance of the zinc-ion battery.

[0038] A preparation method of a nitrogen-doped zinc-ion battery manganese-based cathode material according to the second aspect of the present invention includes the following steps:

[0039] S10: Mix a strong oxidant and a manganese salt and put them into a beaker, add deionized water and stir evenly to form a mixed solution; for example, put the strong oxidant and the manganese salt into the beaker under the action of mechanical stirring.

[0040] S20: Transfer the above mixed solution into a high-pressure reaction kettle with a polytetrafluoroethylene lining and place it in an oven for heating;

[0041] S30: After multiple cycles of cooling - precipitation - filtration - washing, put it into an oven for vacuum drying to obtain the original manganese-based cathode material;

[0042] S40: Weigh the original manganese-based cathode material and hexamethylenetetramine respectively, lay the original manganese-based cathode material flat on the bottom of the reaction kettle lining, and put hexamethylenetetramine into a beaker;

[0043] S50: Put the beaker into the reaction kettle and transfer it into the oven for heating to obtain a surface nitrogen-doped manganese-based cathode material.

[0044] Specifically, S10: Under the action of mechanical stirring, put the strong oxidant and the manganese salt into the beaker, add 50 - 80 mL of deionized water and stir for 0.5 - 1 h; S20: Transfer the above solution into a high-pressure reaction kettle with a polytetrafluoroethylene lining, and then place it in an oven preheated to 120 - 200 °C for heating for 8 - 24 h; S30: After multiple times of cooling, precipitation, filtration and washing, put it into an oven at 80 - 110 °C for vacuum drying to obtain the precursor of the manganese-based cathode material; S40: Weigh the above MnO2 and hexamethylenetetramine at a mass ratio of 1:0.015 - 0.05, then put hexamethylenetetramine into the beaker, and lay MnO2 flat on the bottom of the lining; S50: Put the beaker into the reaction kettle and transfer it into the oven, heat it at 200 °C for 5 h to obtain the surface nitrogen-doped manganese-based compound cathode material.

[0045] This preparation method uses a gas treatment method to treat the surface of the manganese-based cathode material. This method is easy to operate, simple and convenient. Compared with the traditional wet chemical method, the gas treatment method does not require the use of a large amount of solvents, so less waste liquid is generated and the impact on the environment is smaller. At the same time, the gas treatment method is easy to realize continuous and automated production and is suitable for large-scale industrial applications.

[0046] The hexamethylenetetramine gas treatment of this preparation method also affects the charge and discharge reaction process of the manganese-based cathode material. It is found in experimental applications that nitrogen doping is successfully achieved on the surface of the manganese-based cathode material, and the dissolution of manganese is inhibited by bonding with Mn on the surface (N-Mn bond), strengthening the structural stability of the manganese-based cathode material, reducing the internal impedance of the battery, and improving the capacity and rate performance of the zinc-ion battery.

[0047] In an example of the present invention, in the step S10, the strong oxidant and the manganese salt are added in a chemical molar ratio of 4:1 to 6:1.

[0048] In an example of the present invention, in the step S10, the strong oxidant is a permanganate, a persulfate or a peroxide.

[0049] In an example of the present invention, the permanganate is AMnO4, where A is at least one of six metal ions of Li, Na, K, Ca, Mg, and Zn; the persulfate is MS2O8, where M is at least one of three substances of NH4, Na, and K; the peroxide is at least one of two substances of K2O2 and H2O2.

[0050] In an example of the present invention, in the step S10, the manganese salt is at least one of manganese sulfate, manganese acetate, manganese chloride, and manganese carbonate.

[0051] In an example of the present invention, in the step S30, after multiple cycles of cooling - precipitation - filtration - washing, it is placed in an oven at 80 - 110 °C for vacuum drying to obtain the original manganese-based cathode material.

[0052] In an example of the present invention, in the step S40, the mass ratio of the manganese-based oxide to hexamethylenetetramine is 1:0.015 - 0.05.

[0053] In an example of the present invention, in the step S50, the reaction kettle is moved into an oven and heated at 180 - 200 °C to obtain the manganese-based cathode material, and a manganese-based compound cathode material with surface nitrogen doping is formed during the process.

[0054] Application of the positive electrode material prepared by the preparation method of the manganese-based positive electrode material of the zinc ion battery according to the third aspect of the present invention, and the positive electrode material prepared by this preparation method is applied to the positive electrode material of the zinc ion battery or the power battery.

[0055] That is to say, the application of the manganese-based positive electrode material of the aqueous zinc ion battery with surface nitrogen doping as the positive electrode material in the field of zinc ion batteries or power batteries.

[0056] Specific case

[0057] Example 1: The δ-MnO2 positive electrode material is treated with gas using hexamethylenetetramine

[0058] The original manganese-based positive electrode material is directly synthesized by a one-step hydrothermal method. Under mechanical stirring, 12 mmol of potassium permanganate and 2 mmol of manganese sulfate are placed in a beaker, and 60 mL of deionized water is added and stirred for 1 hour. Then, the above solution is transferred into a high-pressure reaction kettle (100 mL) with a polytetrafluoroethylene lining, and then placed in an oven preheated to 160 °C and heated for 12 hours. After cooling, a δ-MnO2 original sample can be obtained, and then it is further precipitated, filtered, and washed with deionized water multiple times and then placed in an oven at 110 °C for vacuum drying. The δ-MnO2 positive electrode material with surface nitrogen doping is obtained by a simple gas treatment method. Weigh 0.0125 g of hexamethylenetetramine and put it into a beaker. Spread 0.5 g of the original manganese-based positive electrode material powder evenly on the bottom of the reaction kettle lining. Transfer the beaker into the reaction kettle and place it in the oven and heat at 200 °C for 5 h to obtain the δ-MnO2 positive electrode material with surface nitrogen doping. Figure 1 XRD patterns of the sample powder before and after treatment are shown. It can be seen that the crystal structure of the sample after treatment has not changed. Figure 2 XPS pictures of the sample powder before and after treatment are shown. It can be seen that the nitrogen doped on the surface of the sample after treatment is bonded to Mn (N-Mn bond). The electrochemical performance is tested using a coin cell. The sample, conductive carbon black, and binder (polyvinylidene fluoride) are mixed at a mass ratio of 7:2:1, and an appropriate amount of solvent NMP (N-methylpyrrolidone) is added. After mixing evenly into a slurry, it is uniformly coated on a titanium foil and vacuum dried at 110 °C to obtain the electrode sheet. Using a metal zinc sheet as the counter electrode, 2 mol·L -1 ZnSO4 and 0.1 mol·L -1 MnSO4 as the electrolyte, and a glass fiber filter paper as the separator (GF-D), the loading of the active material is about 0.8 - 1.5 mg cm -2 , and a 2032-type coin cell is assembled in an air environment. The electrochemical impedance spectrum (EIS) is collected on a CHI 660E electrochemical workstation (Shanghai Chenhua, China). Figure 3The EIS diagram obtained from the test shows that the electrochemical impedance of the battery composed of the cathode material after gas treatment is significantly lower than that of the original cathode material. Using the NEWARE TC53 battery test system, charge-discharge tests were carried out at a constant current density, and the charge-discharge voltage range was 0.8 - 1.8V. The charge-discharge current densities were selected as 200, 500, 1000, and 2000 mA / g respectively. Figure 4 The cyclic performance curves obtained from the test show that the capacities of the cathode material before treatment after cycling at different current densities are 146.5 mAh / g, 83.1 mAh / g, 82.54 mAh / g, and 53.7 mAh / g respectively. The capacities of the treated cathode material after cycling at different current densities are 279.7 mAh / g, 234.4 mAh / g, 174.5 mAh / g, and 113.5 mAh / g respectively. The δ-MnO2 cathode material of the zinc-ion battery treated with hexamethylenetetramine gas shows excellent cyclic performance and rate performance.

[0059] Example 2: The α-MnO2 cathode material was treated with hexamethylenetetramine gas

[0060] The original manganese-based cathode material was directly synthesized by a one-step hydrothermal method. Under mechanical stirring, 5 mmol of potassium persulfate and 5 mmol of manganese sulfate were put into a beaker, and 100 mL of deionized water was added and stirred for 2 hours. Then, the above solution was transferred into a high-pressure reaction kettle (100 mL) with a polytetrafluoroethylene inner lining, and then placed in an oven preheated to 140 °C and heated for 12 hours. After cooling, the α-MnO2 original sample could be obtained. After further precipitation, filtration, and washing with deionized water for multiple times, it was placed in an oven at 80 °C for vacuum drying. The surface nitrogen-doped α-MnO2 cathode material was obtained by a simple gas treatment method. Weighed 0.0125 g of hexamethylenetetramine and put it into a beaker. Spread 0.5 g of the original manganese-based cathode material powder evenly on the bottom of the reaction kettle inner lining. The beaker was transferred into the reaction kettle and placed in the oven together and heated at 200 °C for 5 h to obtain the surface nitrogen-doped α-MnO2 cathode material. The XRD diagrams of the sample powders before and after treatment show that the crystal structures of the samples before and after treatment have not changed. The XPS results of the samples before and after treatment show that the nitrogen doped on the surface of the treated sample is bonded to Mn (N-Mn bond). The electrochemical performance test was carried out using a button cell. The sample, conductive carbon black, and binder (polyvinylidene fluoride) were mixed at a mass ratio of 7:2:1, and an appropriate amount of solvent NMP (N-methylpyrrolidone) was added. After mixing evenly into a slurry, it was evenly coated on the titanium foil and vacuum dried at 110 °C to obtain the electrode sheet. Using a metal zinc sheet as the counter electrode, 2 mol electrode, -1 ZnSO4 and 0.1 mol electrode sheet -1MnSO4 was used as the electrolyte, and glass fiber filter paper was used as the separator (GF-D). The loading of the active material was about 0.8 - 1.5 mg cm -2 , and 2032 coin cells were assembled in an air environment. Electrochemical impedance spectroscopy (EIS) was collected on a CHI 660E electrochemical workstation (Shanghai Chenhua, China). The obtained EIS diagrams showed that the electrochemical impedance of the battery composed of the positive electrode material after gas treatment was significantly lower than that of the original positive electrode material. Using a NEWARE TC53 battery test system, charge-discharge tests were carried out at a constant current density. The charge-discharge voltage range was 0.8 - 1.8 V, and the charge-discharge current densities were selected as 200, 500, 1000, and 2000 mA / g respectively. At charge-discharge currents of 200, 500, 1000, and 2000 mA / g, the capacities of the untreated positive electrode material after charge-discharge (80 cycles at 200 mA / g, 200 cycles at 500 mA / g, 250 cycles at 1000 mA / g, 700 cycles at 2000 mA / g) were 142.5 mAh / g, 80.4 mAh / g, 72.6 mAh / g, and 44.9 mAh / g respectively. The capacities of the treated positive electrode material after cycling at different current densities were 276.5 mAh / g, 231.3 mAh / g, 169.5 mAh / g, and 111.2 mAh / g respectively. The α-MnO2 positive electrode material of the zinc ion battery treated with hexamethylenetetramine gas showed excellent cycle performance and rate performance.

[0061] Example 3: The β-MnO2 positive electrode material was treated with hexamethylenetetramine gas

[0062] The original manganese-based cathode material was directly synthesized by a one-step hydrothermal method. Under mechanical stirring, 1 mL of 38 wt% concentrated hydrochloric acid was added to 50 mL of a 2.5 mmol potassium permanganate aqueous solution and stirred for 30 minutes. Then, the above solution was transferred into a high-pressure reaction kettle (100 mL) with a polytetrafluoroethylene liner and placed in an oven preheated to 140 °C for heating for 12 hours. After cooling, a β-phase original sample could be obtained. After further precipitation, filtration, and washing with deionized water multiple times, it was placed in an oven at 80 °C for vacuum drying. A β-phase nitrogen-doped hollow cathode material with surface nitrogen doping was obtained through a simple gas treatment method. 0.0125 g of hexamethylenetetramine was weighed and placed in a beaker. 0.5 g of the original manganese-based cathode material powder was spread flat on the bottom of the reaction kettle liner. The beaker was transferred into the reaction kettle and placed in the oven for heating at 200 °C for 5 h to obtain a β-phase nitrogen-doped cathode material with surface nitrogen doping. The XRD patterns of the sample powders before and after treatment showed that the crystal structure of the samples did not change before and after treatment. The XPS results of the samples before and after treatment showed that the nitrogen doped on the surface of the treated sample was bonded to Mn (N-Mn bond). The electrochemical performance was tested using a coin cell. The sample, conductive carbon black, and binder (polyvinylidene fluoride) were mixed in a mass ratio of 7:2:1, and an appropriate amount of solvent NMP (N-methylpyrrolidone) was added. After mixing evenly into a slurry, it was uniformly coated on a titanium foil and vacuum dried at 110 °C to obtain the electrode sheet. Using a metal zinc sheet as the counter electrode, 2 mol of -1 ZnSO4 and 0.1 mol of the electrode sheet -1 MnSO4 as the electrolyte, and a glass fiber filter paper as the separator (GF-D), the loading of the active material was about 0.8 - 1.5 mg cm -2, assembled into a 2032 coin cell in an air environment. Electrochemical impedance spectroscopy (EIS) was collected on a CHI 660E electrochemical workstation (Shanghai Chenhua, China). The obtained EIS plots showed that the electrochemical impedance of the cell composed of the gas-treated cathode material was significantly reduced compared to the original cathode material. Using a NEWARE TC53 battery test system, charge-discharge tests were carried out at a constant current density, and the charge-discharge voltage range was 0.8 - 1.8 V. The charge-discharge current densities were selected as 200, 500, 1000, and 2000 mA / g respectively. At charge-discharge currents of 200, 500, 1000, and 2000 mA / g, the capacities of the untreated cathode material after charge-discharge (200 mA / g for 80 cycles, 500 mA / g for 200 cycles, 1000 mA / g for 250 cycles, 2000 mA / g for 700 cycles) were 145.7 mAh / g, 86.4 mAh / g, 75.6 mAh / g, and 41.9 mAh / g respectively. The capacities of the treated cathode material after cycling at different current densities were 266.6 mAh / g, 238.2 mAh / g, 171.5 mAh / g, and 116.8 mAh / g respectively. The zinc ion battery β-amine gas-treated 2 cathode material treated with hexamethylenetetramine gas exhibited excellent cycle performance and rate performance.

[0063] Example 4: The Mn3O4 cathode material was treated with hexamethylenetetramine gas

[0064] The original manganese-based cathode material was directly synthesized by electrodeposition. Using a carbon cloth as the working electrode, 0.1 M Mn(CH3COO)2 and 0.1 M Na2S2O8 as the mixed electrolyte, and a platinum foil as the counter electrode. Then, electrodeposition was carried out at a constant potential of 1.8 V for 20 min to obtain a loading amount of approximately 1.5 mg cm -2Mn3O4. After further precipitation, filtration, and washing with deionized water for multiple times, it was placed in an oven at 110 °C for vacuum drying. The surface nitrogen-doped Mn3O4 cathode material was obtained through a simple gas treatment method. Weighed 0.0125 g of hexamethylenetetramine and put it into a beaker. Spread 0.5 g of the original manganese-based cathode material powder evenly on the bottom of the reaction kettle liner. Moved the beaker into the reaction kettle and placed it in an oven for heating at 200 °C for 5 h to obtain the surface nitrogen-doped Mn3O4 cathode material. The XRD patterns of the sample powders before and after treatment showed that the crystal structures of the samples before and after treatment did not change. The XPS results of the samples before and after treatment showed that the nitrogen doped on the surface of the treated sample was bonded to Mn (N-Mn bond). The electrochemical performance was tested using a coin cell. The sample, conductive carbon black, and binder (polyvinylidene fluoride) were mixed at a mass ratio of 7:2:1, and an appropriate amount of solvent NMP (N-methylpyrrolidone) was added. After mixing evenly into a slurry, it was uniformly coated on a titanium foil and vacuum dried at 110 °C to obtain the electrode sheet. Using a metal zinc sheet as the counter electrode, 2 mol of -1 ZnSO4 and 0.1 mol of the electrode sheet -1 MnSO4 as the electrolyte, and a glass fiber filter paper as the separator (GF-D). The loading of the active material was about 0.8 - 1.5 mg cm -2 , and a 2032-type coin cell was assembled in an air environment. The electrochemical impedance spectrum (EIS) was collected on a CHI 660E electrochemical workstation (Shanghai Chenhua, China). The EIS diagram obtained from the test showed that the electrochemical impedance of the battery composed of the cathode material after gas treatment was significantly reduced compared with the original cathode material. Using a NEWARE TC53 battery test system, charge-discharge tests were carried out at a constant current density. The charge-discharge voltage range was 0.8 - 1.8 V, and the charge-discharge current densities were selected as 200, 500, 1000, and 2000 mA / g respectively. At charge-discharge currents of 200, 500, 1000, and 2000 mA / g, the capacities of the untreated cathode material after charge-discharge (cycled 80 times at 200 mA / g, 200 times at 500 mA / g, 250 times at 1000 mA / g, and 700 times at 2000 mA / g) were 141.2 mAh / g, 82.3 mAh / g, 73.8 mAh / g, and 51.2 mAh / g respectively. The capacities of the treated cathode material after cycling at different current densities were 262.1 mAh / g, 232.1 mAh / g, 174.1 mAh / g, and 110.4 mAh / g respectively. The Mn3O4 cathode material of the zinc-ion battery treated with hexamethylenetetramine gas showed excellent cycle performance and rate performance.

[0065] Example 5: The λ-MnO2 cathode material was treated with hexamethylenetetramine gas

[0066] The original manganese-based cathode material was synthesized by one-step hydrothermal method plus calcination. Under mechanical stirring, 2.5 g of potassium permanganate and 1.5 g of manganese acetate were placed in a beaker, and 100 mL of deionized water was added and stirred for 30 minutes. Then, the above solution was transferred into a high-pressure reaction kettle (100 mL) with a polytetrafluoroethylene lining, and then placed in an oven preheated to 180 °C and heated for 12 hours. After cooling, it was precipitated, filtered and washed with deionized water for several times, placed in an oven at 80 °C for vacuum drying, and then placed in an oven for calcination at 450 °C for 5 h to obtain the calcined original sample. The surface nitrogen-doped cathode material was obtained by a simple gas treatment method. Weighed 0.0125 g of hexamethylenetetramine and placed it in a beaker. Spread 0.5 g of the original manganese-based cathode material powder evenly on the bottom of the reaction kettle lining. The beaker was transferred into the reaction kettle and placed in an oven for heating at 200 °C for 5 h to obtain the surface nitrogen-doped cathode material. The XRD patterns of the sample powders before and after treatment showed that the crystal structure of the samples did not change before and after treatment. The XPS results of the samples before and after treatment showed that the nitrogen doped on the surface of the treated sample was bonded to Mn (N-Mn bond). The electrochemical performance was tested using a coin cell. The sample, conductive carbon black and binder (polyvinylidene fluoride) were mixed at a mass ratio of 7:2:1, and an appropriate amount of solvent NMP (N-methylpyrrolidone) was added. After mixing evenly into a slurry, it was evenly coated on a titanium foil and vacuum dried at 110 °C to obtain the electrode sheet. Using a metal zinc sheet as the counter electrode, 2 mol of -1 ZnSO4 and 0.1 mol of the electrode sheet -1 MnSO4 as the electrolyte, and a glass fiber filter paper as the separator (GF-D). The loading of the active material was about 0.8 - 1.5 mg cm -2, assembled into a 2032 coin cell in an air environment. Electrochemical impedance spectroscopy (EIS) was collected on a CHI 660E electrochemical workstation (Shanghai Chenhua, China). The obtained EIS plots showed that the electrochemical impedance of the cell composed of the gas-treated cathode material was significantly reduced compared to the original cathode material. Using a NEWARE TC53 battery test system, charge-discharge tests were carried out at a constant current density, and the charge-discharge voltage range was 0.8 - 1.8 V. The charge-discharge current densities were selected as 200, 500, 1000, and 2000 mA / g respectively. At charge-discharge currents of 200, 500, 1000, and 2000 mA / g, the capacities of the untreated cathode material after charge-discharge (200 mA / g for 80 cycles, 500 mA / g for 200 cycles, 1000 mA / g for 250 cycles, 2000 mA / g for 700 cycles) were 139.2 mAh / g, 77.3 mAh / g, 72.2 mAh / g, and 50.4 mAh / g respectively. The capacities of the treated cathode material after cycling at different current densities were 256.8 mAh / g, 231.3 mAh / g, 177.7 mAh / g, and 115.4 mAh / g respectively. The cathode material of the zinc ion battery treated with hexamethylenetetramine gas showed excellent cycle performance and rate performance.

[0067] The above-described exemplary embodiments of a nitrogen-doped zinc ion battery manganese-based cathode material and its preparation method and application proposed by the present invention were described in detail with reference to preferred embodiments. However, those skilled in the art can understand that, without departing from the concept of the present invention, various modifications and alterations can be made to the above specific embodiments, and various combinations of the technical features and structures proposed by the present invention can be made, without exceeding the protection scope of the present invention. The protection scope of the present invention is determined by the appended claims.

Claims

1. A nitrogen-doped manganese-based cathode material for zinc-ion batteries, characterized in that, The positive electrode material is a manganese-based compound doped with N ions on the surface. Among them, the manganese-based compound includes at least one of the nine types: α-MnO2, β-MnO2, γ-MnO2, δ-MnO2, T-MnO2, λ-MnO2, Mn2O3, Mn3O4, and ZnMn2O4.

2. The preparation method of the nitrogen-doped zinc-ion battery manganese-based cathode material according to claim 1, characterized in that, It includes the following steps: S10: Mix a strong oxidant and a manganese salt in a beaker, add deionized water and stir evenly to form a mixed solution; S20: Transfer the above mixed solution into a high-pressure reaction kettle with a polytetrafluoroethylene liner and place it in an oven for heating; S30: After multiple cycles of cooling - precipitation - filtration - washing, place it in an oven for vacuum drying to obtain the original manganese-based positive electrode material; S40: Weigh the original manganese-based positive electrode material and hexamethylenetetramine respectively. Spread the original manganese-based positive electrode material flat on the bottom of the reaction kettle liner and put hexamethylenetetramine in a beaker; S50: Place the beaker in the reaction kettle and transfer it to an oven for heating to obtain a manganese-based positive electrode material doped with nitrogen on the surface.

3. The preparation method of the nitrogen-doped manganese-based positive electrode material for a zinc-ion battery according to claim 2, wherein in the step S10, the strong oxidant and the manganese salt are added in a chemical molar ratio of 4:1 to 6:

1.

4. The preparation method of the nitrogen-doped manganese-based positive electrode material for a zinc-ion battery according to claim 2, wherein in the step S10, the strong oxidant is a permanganate, a persulfate or a peroxide.

5. The preparation method of the nitrogen-doped manganese-based positive electrode material for a zinc-ion battery according to claim 4, wherein the permanganate is AMnO4, where A is at least one of the six metal ions: Li, Na, K, Ca, Mg, and Zn; the persulfate is MS2O8, where M is at least one of the three substances: NH4, Na, and K; the peroxide is at least one of the two substances: K2O2 and H2O2.

6. The preparation method of the nitrogen-doped manganese-based positive electrode material for a zinc-ion battery according to claim 2, wherein in the step S10, the manganese salt is at least one of manganese sulfate, manganese acetate, manganese chloride, and manganese carbonate.

7. The preparation method of the nitrogen-doped manganese-based positive electrode material for a zinc-ion battery according to claim 2, wherein in the step S30, after multiple cycles of cooling - precipitation - filtration - washing, place it in an oven at 80 - 110 °C for vacuum drying to obtain the original manganese-based positive electrode material.

8. The preparation method of the nitrogen-doped manganese-based positive electrode material for a zinc-ion battery according to claim 2, wherein in the step S40, the mass ratio of the manganese-based oxide to hexamethylenetetramine is 1:0.015 to 0.

05.

9. The preparation method of the nitrogen-doped manganese-based positive electrode material for a zinc-ion battery according to claim 2, wherein in the step S50, transfer the reaction kettle to an oven and heat it at 180 - 200 °C to obtain the manganese-based positive electrode material.

10. Application of preparing a cathode material by using the preparation method of a nitrogen-doped zinc-ion battery manganese-based cathode material according to any one of claims 2 to 9, characterized in that, The positive electrode material prepared by this preparation method is applied to the positive electrode material of a zinc-ion battery or a power battery.

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