Pre-sodium treated copper-zinc based sodium-ion battery cathode material and method for manufacturing the same.

Abstract

To provide a pre-sodium treated positive electrode material for a copper-zinc-based sodium ion battery and a method of preparing the same.SOLUTION: A method includes: obtaining a mixed solution containing copper-zinc-based elements through wet pre-sodium treatment; then conducting spray drying of the mixed solution containing copper-zinc-based elements to obtain precursor powder of a positive electrode material for a copper-zinc-based sodium ion battery; and then mixing the precursor powder with a sodium source for sintering, coating and crushing to obtain a positive electrode material for a copper-zinc-based sodium ion battery. A positive electrode material for a battery of the present invention introduces weakly oxidizing zinc and nickel elements based on a copper-based material, and reduces the use of highly oxidizing copper and iron elements. After the material is prepared into a battery, the oxidation of metal ions in an electrochemical environment is reduced overall, so that the oxidation of copper ions to an electrolyte is greatly reduced, CO2 gas generated by oxidation and decomposition of the electrolyte is reduced, the electrochemical environment is stabilized, and the electrical performance of the battery is improved.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a presodized copper-zinc based sodium-ion battery cathode material and a method for producing the same, and belongs to the technical field of sodium-ion batteries. [Background technology]

[0002] In 2014, Hu Yongsheng et al. from China studied Cu in layered oxides. 3+ / Cu 2+ We were the first to discover the electrochemical activity of redox pairs and designed and manufactured a series of low-cost copper-based cathode materials. After nearly a decade of tireless effort, copper-based sodium-ion battery cathode materials and sodium-ion batteries have been put into trial operation, but these trials have not met the designers' expectations.

[0003] When copper-based cathode materials are used in sodium-ion batteries, their specific capacity is low, resulting in low energy density and failing to meet consumer demands for higher energy density. Conversely, when copper-based cathode materials are used in batteries, the strong oxidative properties of divalent copper ions in the electrochemical environment make the electrolyte susceptible to oxidative decomposition, generating CO2 gas. As the cycle progresses, the electrolyte undergoes continuous oxidative decomposition, generating more CO2 gas and degrading the battery's electrical performance. Therefore, while copper-based cathode materials offer performance advantages in short cycles, their performance deteriorates rapidly in long cycles due to increased gas generation. Consequently, there is a need to develop sodium-ion battery cathode materials with higher specific capacity and lower gas generation.

[0004] As a result of continuous research and development and improvements by scientists, nickel-iron-manganese-based sodium-ion battery cathode materials have been developed in recent years. Compared to copper-based materials, this material has a higher specific capacity and slightly lower cycle gas generation under the same voltage conditions. However, it is expensive due to the large amount of precious nickel metal used, limiting its large-scale use. Therefore, there is still a need to develop sodium-ion battery cathode materials that are low-cost, have high specific capacity, and produce less cycle gas. [Overview of the project] [Problems that the invention aims to solve]

[0005] In view of the shortcomings of the prior art, the present invention proposes a pre-sodium-treated copper-zinc-based sodium-ion battery cathode material and a method for producing the same, which inherits the excellent cycle performance of copper-based materials while significantly reducing gas generation during the cycling process and promoting large-scale application of sodium-ion battery cathode materials.

[0006] The present invention provides a technical solution for producing a pre-sodium-treated copper-zinc-based sodium-ion battery cathode material, comprising the steps of: S1: Wet pre-sodium treatment: Add zinc salt, copper salt, iron salt, M source and sodium salt to a measuring cup according to stoichiometric ratios of 0.78~1.0:0.02~0.08:0.25~0.36:0.58~0.65:0.01~0.08, stir to dissolve, and obtain a mixed salt solution; also, place the mixed salt solution with copper oxide or zinc oxide in a sand mill and sand for a certain period of time to obtain a mixed solution containing copper-zinc-based elements; S2: Spray-dry the mixed solution containing copper-zinc-based elements from S1 to obtain a precursor powder of the copper-zinc-based sodium-ion battery cathode material; S3: Mix the precursor powder from S2 with a sodium source and sinter, add an N source for coating treatment, and finally pulverize to obtain the copper-zinc-based sodium-ion battery cathode material.

[0007] In the above method, the copper oxide is copper oxide, the zinc oxide is zinc oxide, the nickel salt or manganese salt is a carbonate, sulfate, oxalate, or acetate, the iron salt is ferrous sulfate heptahydrate, ferrous sulfate monohydrate, ferrous oxalate, or ferrous chloride, the copper salt is anhydrous copper sulfate or copper sulfate pentahydrate, and the zinc salt is anhydrous zinc sulfate, zinc sulfate monohydrate, or zinc sulfate heptahydrate.

[0008] In the above method, during the sanding process, a corresponding amount is weighed out in a mass ratio of material:water:zirconium beads = 1-1.5:3-5:2-5.0.

[0009] In the above method, in step S1, the molar ratio of sodium element content to total metal element content is 0.05 to 0.5, and the sodium source is sodium carbonate, sodium hydroxide, sodium bicarbonate, sodium acetate, sodium nitrate, or sodium chloride.

[0010] In the above method, the N source is one or more selected from Ca, Ti, Mg, Al, W, Zr, Sr, B, Ba, Ce, Mo, Co, La, Si, P, S, or Li.

[0011] In the above method, the sintering is carried out in two stages, with the first sintering temperature being 870°C to 945°C and the second sintering temperature being 300°C to 800°C.

[0012] In the above method, the coating method may be a solid-phase method or a liquid-phase method.

[0013] In the above method, the grinding method may be a ball mill, mechanical grinding, or air-jet grinding, and the particle size of the copper-zinc based sodium ion battery cathode material after grinding is such that the median particle size D50 is 5.2 to 14 μm.

[0014] In the above method, the chemical formula of the pre-sodium-treated copper-zinc based sodium-ion battery cathode material is: Na m Cu x Zny Fe z M 1-x-y-z The molecule is O2, where 0.75 ≤ m ≤ 1.08, and the M source is one or more selected from Ni, Co, Mn, Ca, Ti, Mg, Al, W, Zr, Sr, B, Ba, Ce, Mo, La, Si, P, S, or Li, where 0.005 ≤ x ≤ 0.10, 0.005 ≤ y ≤ 0.09, and 0.20 ≤ z ≤ 0.45.

[0015] Simultaneously, the present invention also provides a pre-sodium-treated copper-zinc-based sodium-ion battery cathode material manufactured by the method for manufacturing the pre-sodium-treated copper-zinc-based sodium-ion battery cathode material described above.

[0016] Another object of the present invention is to provide a sodium-ion battery cathode containing the above-mentioned copper-zinc based sodium-ion battery cathode material as a cathode active material.

[0017] Another object of the present invention is to provide a sodium-ion battery comprising the above-mentioned sodium-ion battery positive electrode, negative electrode, and electrolyte containing a sodium salt.

[0018] The sodium-ion batteries described above are used as power sources in distributed energy storage systems, power tools, or electric vehicles.

[0019] Another object of the present invention is to provide a power system, energy storage system, or removable storage device manufactured by the sodium-ion battery described above. [Effects of the Invention]

[0020] The advantages of the present invention, achieved by adopting the above technical solutions, are as follows:

[0021] 1. The pre-sodiumated copper-zinc-based sodium-ion battery cathode material provided by the present invention is based on a copper-based material, introduces zinc and nickel elements with weak oxidizing properties, reduces the use of copper and iron elements with strong oxidizing properties, and after this material is manufactured into a battery, the oxidizing property of metal ions in the electrochemical environment is reduced as a whole, thereby greatly reducing the oxidation of copper ions to the electrolyte, reducing the CO2 gas generated by the oxidative decomposition of the electrolyte, stabilizing the electrochemical environment, and improving the electrical performance of the battery.

[0022] 2. The manufacturing method of the present invention introduces sanding and pre-sodiumation treatment, which is different from the conventional sanding method. In the conventional manufacturing method, although sintering provides sufficient power for the diffusion of sodium ions, its effect is not yet ideal. Also, since the ionic radius of sodium is larger than the radii of copper ions, zinc ions, manganese ions, iron ions, and nickel ions, in order to sufficiently diffuse sodium ions into the matrix materials with smaller ionic radii, it is necessary to provide a higher sintering temperature, a sufficiently long sintering time, or adopt a distributed diffusion method. In contrast, the present invention puts a part of the sodium source into the sanding process, grinds the particle size of the sodium source smaller by sanding, and at the same time introduces the sodium source when manufacturing the precursor, so that the distribution of the sodium source becomes more uniform from the inside to the outside of the material, leading to better diffusion and movement of sodium ions in the subsequent sintering process, and more sufficient occupation of sodium ions inside the material structure.

[0023] 3. By performing spray drying treatment after sanding, the moisture content of the material is reduced, and it becomes difficult for sodium ions inside the material to be converted into sodium carbonate, which is advantageous for reducing the residual sodium content of the material, especially the sodium carbonate content in the residual sodium.

Brief Description of the Drawings

[0024] [Figure 1] It is a comparison diagram of the discharge cycles of the cathode materials prepared in Examples 1 to 6 and Comparative Example 1. [Modes for carrying out the invention]

[0025] All raw materials and reagents used in this invention are purchased from mainstream manufacturers on the market, and unless the manufacturer or concentration is specified, they can all be substituted with conventional raw materials and reagents, and there are no particular limitations as long as the intended effect is achieved. All equipment and apparatus used in this embodiment are purchased from major manufacturers on the market and are not particularly limited as long as the intended effect is achieved. Unless specific techniques or conditions are specified in this embodiment, the techniques or conditions described in the literature in the art or the product instruction manuals shall be followed. Table 1 shows the sources of raw materials and equipment used in the embodiments and comparative examples of this invention.

[0026] [Table 1]

[0027] In the embodiments of the present invention, the particle size test of the sodium ion cathode material refers to the National Standard GB / T19077-2016 Particle Size Distribution Laser Diffraction Method of the People's Republic of China. Test equipment: Malvern, Master Size 2000 laser particle size analyzer. Test procedure: 1 g of powder is weighed, added to 60 ml of pure water, and after irradiating with external ultrasound for 5 mins, the sample is poured into an injector, the test is performed, and the test data is recorded. Test conditions: The test principle is Mie theory (light scattering), the detection angle is 0 to 135°, the external ultrasound intensity is 40 kHz, 180 watts, the refractive index of the particles is 1.692, the absorptivity of the particles is 1, the sample test time is 6 s, the number of background test snaps is 6000 times, and the light shielding degree is 8 to 12%.

[0028] Among them, the test method for free sodium (residual alkali) in the sodium ion cathode material in the embodiments of the present invention is as follows. That is, accurately weigh 30 g ± 0.01 g of the sample, put it into a 250 mL conical flask, and put a magnet in it, then add 100 mL of deionized water. Place it on a magnetic stirrer, turn on the stirrer and stir for 30 minutes. Filter the mixed solution with qualitative filter paper and a funnel. Transfer 1 mL of the filtrate to a 100 mL beaker and put a magnet in it. Place the beaker on a magnetic stirrer, and add 2 drops of phenolphthalein indicator. Titrate with 0.05 mol / L hydrochloric acid standard titrant until the color of the solution changes from red to colorless (V 初期 = 0), and record the volume V1 of 0.05 mol / L hydrochloric acid standard titrant (endpoint 1, V1 = V 終点1 -V 初期 ). Add 2 drops of methyl red indicator, and the color of the solution changes from colorless to yellow. Titrate with 0.05 mol / L hydrochloric acid standard titrant until the color of the solution changes from yellow to orange. Place the beaker in a heating furnace and heat until the solution boils (the color of the solution changes from orange to yellow). Take out the beaker and cool it to room temperature, then place the beaker on a magnetic stirrer and titrate with 0.05 mol / L hydrochloric acid standard titrant until the color of the solution changes from yellow to light red, and record the volume V2 of 0.05 mol / L hydrochloric acid standard titrant (endpoint 2, V2 = V 終点2 - V終点1 ).

[0029] The calculation formula for the free sodium content is as follows.

[0030]

Number

[0031] M is the relative atomic mass of sodium, M1 is the relative atomic mass of sodium carbonate, M2 is the relative atomic mass of sodium hydroxide, m is the mass of the sample / g, V1 is the first titration endpoint / mL, V2 is the second titration endpoint / mL, c is the concentration of the hydrochloric acid standard titrant / mol / L, and 100 in the numerator represents the dilution ratio.

[0032] In the embodiments of the present invention, the pH value of the sodium ion cathode material is measured using a PHSJ-3F magnetic pH meter, and the specific method is as follows: Accurately weigh 5 g ± 0.05 g of the sample, add deionized water in a mass ratio of material to water of 1:9 to prepare a 10% suspension, then place a magnet inside and put it on the tray of a magnetic stirrer, and stir for 5 minutes at a rotation speed of 880 r / min. Filter the mixed solution through qualitative filter paper and a funnel, and place it in a constant temperature water bath set to 25°C, and filter at constant temperature for 20 ± 5 minutes. Rinse the electrode with the sample solution, and after that, insert the electrode and temperature sensor into the sample solution, and when the measured value stabilizes and shows a temperature of 25°C, record the pH value.

[0033] The sodium-ion battery of the present invention consists of electrodes, an electrolyte, a separator, and an aluminum plastic film. Specifically, the electrodes include a positive electrode and a negative electrode. The positive electrode is manufactured from a material comprising a positive electrode current collector, a positive electrode active material coated on the positive electrode current collector, a binder, a conductive additive, etc., and the positive electrode active material is the pre-sodium-treated copper-zinc based sodium-ion battery positive electrode material of the present invention. The negative electrode is manufactured from a material comprising a current collector, a negative electrode active material coated on the current collector, a binder, a conductive additive, etc. The separator is a PP / PE film commonly used in this industry and is used to separate the positive electrode and the negative electrode from each other. The aluminum plastic film is a housing for the positive electrode, negative electrode, separator, and electrolyte.

[0034] The binder in this invention is primarily used to improve the binding properties between positive electrode active material particles and between positive electrode active material particles and the current collector. The binder in this invention can be any commercially available binder used in the industry. Specifically, the binder may be selected from polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymer, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylic acid (esterified) styrene-butadiene rubber, epoxy resin, nylon, or compositions thereof.

[0035] The conductive additive in the present invention can be any commercially available conductive additive commonly used in the industry. Specifically, the conductive additive may be selected from carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, Ketjenblack, or carbon fibers), metal-based materials (e.g., metal powders or metal fibers containing copper, nickel, aluminum, silver, etc.), conductive polymers (e.g., polyphenylene derivatives), or compositions thereof.

[0036] In the following examples, the specific procedure for manufacturing a sodium-ion button battery using the positive electrode material of the present invention is as follows.

[0037] Manufacturing of the positive electrode: The positive electrode material of the present invention, the binder polyvinylidene fluoride (PVDF), and conductive carbon black (SP) are thoroughly mixed in a weight ratio of 7:2:1, stirred to form a uniform slurry, applied to an aluminum foil current collector, dried, and pressed to form an electrode sheet. The pressed positive electrode sheet is punched out, weighed, and fired, and then the battery is assembled in a vacuum glove box. First, the bottom of the button cell shell is placed, nickel foam (2.5 mm) and a negative electrode metallic sodium sheet (manufacturer: Shenzhen Youyan Technology Co., Ltd.) are placed on top of the bottom of the shell, and 0.5 g of electrolyte is injected in an environment with a relative humidity of less than 1.5%. The electrolyte is a mixed solvent of ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC) in a mass ratio of 1:1:1, and the electrolyte is a 1 mol / L sodium hexafluoride phosphate solution. Place the separator and positive electrode sheet, then cover it with the button cell's shell cover to seal it. The button cell's model number is CR2430.

[0038] The technical solutions of the present invention will be described in more detail below with reference to specific embodiments and accompanying drawings.

[0039] Example 1 Sodium carbonate, zinc sulfate heptahydrate, ferrous sulfate heptahydrate, manganese sulfate, nickel sulfate, and copper oxide were weighed in equivalent amounts using stoichiometric ratios Na:Zn:Fe:Mn:Ni:Cu = 1.0:0.02:0.25:0.35:0.3:0.08.

[0040] S1: Pre-sodiumization by wet process: Zinc sulfate heptahydrate, ferrous sulfate heptahydrate, manganese sulfate, nickel sulfate, and sodium carbonate (sodium carbonate added at a rate of 40% of the weighed weight) were dissolved in water (the weight of the water was recorded) according to the weighed weight to prepare a salt solution for use. The salt solution, which had been dissolved with copper oxide, was weighed in an equivalent amount in a mass ratio of material:water:zirconium beads = 1.5:4.5:3.5, placed in a sand mill, and sanded for 30 minutes to obtain a mixed solution containing copper-zinc based elements.

[0041] A mixture containing S2:S1 copper-zinc based elements was spray-dried to obtain a pre-sodium-treated copper-zinc based sodium-ion battery cathode material precursor powder.

[0042] The S3:S2 precursor powder and sodium carbonate (where the amount of sodium carbonate is the remaining amount of the weight initially weighed according to the stoichiometric ratio) were mixed, and the homogeneously mixed material was incubated at 870°C in an air atmosphere for 20 hours, then allowed to cool naturally, and ground using a super micro stone disc mill with a disc spacing of 1.0 mm and a rotation speed of 1800 r / min to obtain a semi-finished product. Next, magnesium oxide was weighed and placed in a ball mill with the above semi-finished product and magnesium source (elemental magnesium) in a molar ratio of 1:0.004, and ball milled at a frequency of 40 Hz for 30 minutes to obtain a homogeneously mixed material. The material was incubated at 700°C in an air atmosphere for 5 hours, then allowed to cool naturally, and then ball milled and sieved to obtain pre-sodium-treated copper-zinc based sodium-ion battery cathode material A1.

[0043] For the sodium-ion battery cathode material A1 of this embodiment, the particle size, pH value, and sodium carbonate content in the free sodium were tested. Furthermore, A1 was manufactured into a button cell and cycle tests were performed. The cycle curve at 0.5C under conditions of 4.0 to 2.0V is shown in detail in Figure 1.

[0044] Example 2 Sodium carbonate, zinc sulfate heptahydrate, ferrous sulfate heptahydrate, manganese sulfate, nickel sulfate, and copper oxide were weighed in equivalent amounts using stoichiometric ratios Na:Zn:Fe:Mn:Ni:Cu = 1.0:0.02:0.33:0.30:0.3:0.05.

[0045] S1: Pre-wet sodium treatment: Zinc sulfate heptahydrate, ferrous sulfate heptahydrate, manganese sulfate, nickel sulfate, and sodium carbonate (only 60% of the weighed weight of sodium carbonate was added) were dissolved in water (the weight of the water was recorded) according to the weighed weight to prepare a salt solution for use. The salt solution, which had been dissolved with copper oxide, was weighed in an equivalent amount in a mass ratio of material:water:zirconium beads = 1.5:5.0:3.0, placed in a sand mill, and sanded for 50 minutes to obtain a mixed solution containing copper-zinc based elements.

[0046] A mixture containing S2:S1 copper-zinc based elements was spray-dried to obtain a pre-sodium-treated copper-zinc based sodium-ion battery cathode material precursor powder.

[0047] The precursor powder of S3:S2 and sodium carbonate (where the amount of sodium carbonate is the remaining amount of the weight initially weighed according to the stoichiometric ratio) were mixed, and the homogeneously mixed material was incubated at 880°C in an air atmosphere for 18 hours, then allowed to cool naturally, and ball milled at 50Hz for 20 minutes to obtain a semi-finished product. Next, aluminum oxide was weighed and placed in a ball mill with the above semi-finished product in a molar ratio of 1:0.002 of aluminum source (aluminum element), and ball milled at 50Hz for 30 minutes to obtain a homogeneously mixed material, incubated at 650°C in an air atmosphere for 6 hours, then allowed to cool naturally, and then ball milled and sieved to obtain pre-sodium-treated copper-zinc based sodium-ion battery cathode material A2.

[0048] For the sodium-ion battery cathode material A2 of this embodiment, the particle size, pH value, and sodium carbonate content in the free sodium were tested. Furthermore, A2 was manufactured into a button cell and cycle tests were performed. The cycle curve at 0.5C under conditions of 4.0 to 2.0V is shown in detail in Figure 1.

[0049] Example 3 Sodium carbonate, zinc sulfate heptahydrate, ferrous sulfate heptahydrate, manganese sulfate, nickel sulfate, and copper oxide were weighed in equivalent amounts using stoichiometric ratios Na:Zn:Fe:Mn:Ni:Cu = 1.0:0.03:0.36:0.33:0.25:0.03.

[0050] S1: Pre-wet sodium treatment: Zinc sulfate heptahydrate, ferrous sulfate heptahydrate, manganese sulfate, nickel sulfate, and sodium carbonate (only 30% of the weighed weight of sodium carbonate was added) were dissolved in water (the weight of the water was recorded) according to the weighed weight to prepare a salt solution for use. The salt solution, which had been dissolved with copper oxide, was weighed in an equivalent amount in a mass ratio of material:water:zirconium beads = 1.2:5.0:3.0, placed in a sand mill, and sanded for 40 minutes to obtain a mixed solution containing copper-zinc based elements.

[0051] A mixture containing S2:S1 copper-zinc based elements was spray-dried to obtain a pre-sodium-treated copper-zinc based sodium-ion battery cathode material precursor powder.

[0052] The precursor powder of S3:S2 and sodium carbonate (where the amount of sodium carbonate is the remaining amount after the initial weighing according to the stoichiometric ratio) were mixed, and the homogeneously mixed material was kept at a constant temperature of 910°C in an air atmosphere for 12 hours, then allowed to cool naturally, and ball milled at 50 Hz for 10 minutes to obtain a semi-finished product. Next, boric acid was weighed and placed in a ball mill in a molar ratio of 1:0.002 with the above semi-finished product and boron source (element boron), and ball milled at a frequency of 40 Hz for 20 minutes to obtain a homogeneously mixed material, kept at a constant temperature of 300°C in an air atmosphere for 3 hours, then allowed to cool naturally, and then ball milled and sieved to obtain pre-sodium-treated copper-zinc based sodium-ion battery cathode material A3.

[0053] For the sodium-ion battery cathode material A3 of this embodiment, the particle size, pH value, and sodium carbonate content in the free sodium were tested. Furthermore, A3 was manufactured into a button cell and cycle tests were performed. The cycle curve at 0.5C under conditions of 4.0 to 2.0V is shown in detail in Figure 1.

[0054] Example 4 Sodium carbonate, copper sulfate pentahydrate, ferrous sulfate heptahydrate, manganese sulfate, nickel sulfate, and zinc oxide were weighed in equivalent amounts using stoichiometric ratios Na:Zn:Fe:Mn:Ni:Cu = 0.78:0.04:0.35:0.34:0.25:0.04.

[0055] S1: Pre-wet sodium treatment: Copper sulfate pentahydrate, ferrous sulfate heptahydrate, manganese sulfate, nickel sulfate, and sodium carbonate (only 50% of the weighed weight of sodium carbonate was added) were dissolved in water (the weight of the water was recorded) according to the weighed weight to prepare a salt solution for use. The salt solution, which had been dissolved with zinc oxide, was weighed in an equivalent amount in a mass ratio of material:water:zirconium beads = 1.0:3.0:3.0, placed in a sand mill, and sanded for 20 minutes to obtain a mixed solution containing copper-zinc based elements.

[0056] A mixture containing S2:S1 copper-zinc based elements was spray-dried to obtain a pre-sodium-treated copper-zinc based sodium-ion battery cathode material precursor powder.

[0057] The S3:S2 precursor powder and sodium carbonate (where the amount of sodium carbonate is the remaining amount after the initial weighing according to the stoichiometric ratio) were mixed, and the homogeneously mixed material was incubated at 930°C in an air atmosphere for 10 hours, then allowed to cool naturally, and ball milled at 42 Hz for 40 minutes to obtain a semi-finished product. Next, ammonium dihydrogen phosphate was weighed and placed in a ball mill in a molar ratio of 1:003 with the above semi-finished product and phosphorus source (phosphorus element), and ball milled at 48 Hz for 25 minutes to obtain a homogeneously mixed material. The material was incubated at 450°C in an air atmosphere for 4.5 hours, then allowed to cool naturally, and then ball milled and sieved to obtain pre-sodium-treated copper-zinc based sodium-ion battery cathode material A4.

[0058] For the sodium-ion battery cathode material A4 of this embodiment, the particle size, pH value, and sodium carbonate content in the free sodium were tested. Furthermore, A4 was manufactured into a button cell and cycle tests were performed. The cycle curve at 0.5C under conditions of 4.0 to 2.0V is shown in detail in Figure 1.

[0059] Example 5 Sodium carbonate, copper sulfate pentahydrate, ferrous sulfate heptahydrate, manganese oxalate, nickel oxalate, and zinc oxide were weighed in equivalent amounts using stoichiometric ratios Na:Zn:Fe:Mn:Ni:Cu = 0.93:0.04:0.31:0.38:0.22:0.04.

[0060] S1: Pre-wet sodium treatment: Copper sulfate pentahydrate, ferrous sulfate heptahydrate, manganese sulfate, nickel sulfate, and sodium carbonate (only 35% of the weighed weight of sodium carbonate was added) were dissolved in water (the weight of the water was recorded) according to the weighed weight to prepare a salt solution for use. The salt solution, which had been dissolved with zinc oxide, was weighed in an equivalent amount in a mass ratio of material:water:zirconium beads = 1.3:3.8:3.0, placed in a sand mill, and sanded for 45 minutes to obtain a mixed solution containing copper-zinc based elements.

[0061] A mixture containing S2:S1 copper-zinc based elements was spray-dried to obtain a pre-sodium-treated copper-zinc based sodium-ion battery cathode material precursor powder.

[0062] The S3:S2 precursor powder and sodium carbonate (where the amount of sodium carbonate is the remaining amount of the weight initially weighed according to the stoichiometric ratio) were mixed, and the homogeneously mixed material was incubated at 900°C in an air atmosphere for 16 hours, then allowed to cool naturally, and ground using a super micro stone disc mill with a disc spacing of 0.4 mm and a rotation speed of 2500 r / min to obtain a semi-finished product. Next, niobium pentoxide was weighed and placed in a ball mill in a molar ratio of 1:0.005 with the above semi-finished product and niobium source (element niobium), and ball milled at a frequency of 35 Hz for 45 minutes to obtain a homogeneously mixed material. The material was incubated at 630°C in an air atmosphere for 8.5 hours, then allowed to cool naturally, and then ball milled and sieved to obtain pre-sodium-treated copper-zinc based sodium-ion battery cathode material A5.

[0063] For the sodium-ion battery cathode material A5 of this embodiment, the particle size, pH value, and sodium carbonate content in the free sodium were tested. Furthermore, A5 was manufactured into a button cell and cycle tests were performed. The cycle curve at 0.5C under conditions of 4.0 to 2.0V is shown in detail in Figure 1.

[0064] Example 6 Sodium carbonate, copper sulfate pentahydrate, ferrous sulfate heptahydrate, manganese carbonate, nickel carbonate, and zinc oxide were weighed in equivalent amounts using the stoichiometric ratio Na:Zn:Fe:Mn:Ni:Cu = 0.88:0.08:0.30:0.38:0.22:0.01.

[0065] S1: Pre-wet sodium treatment: Copper sulfate pentahydrate, ferrous sulfate heptahydrate, manganese carbonate, nickel carbonate, and sodium carbonate (only 25% of the weighed weight of sodium carbonate was added) were dissolved in water (the weight of the water was recorded) according to the weighed weight to prepare a salt solution for use. The salt solution, which had been dissolved with zinc oxide, was weighed in an equivalent amount in a mass ratio of material:water:zirconium beads = 1.5:5.0:4.3, placed in a sand mill, and sanded for 90 minutes to obtain a mixed solution containing copper-zinc based elements.

[0066] A mixture containing S2:S1 copper-zinc based elements was spray-dried to obtain a pre-sodium-treated copper-zinc based sodium-ion battery cathode material precursor powder.

[0067] The S3:S2 precursor powder and sodium carbonate (where the amount of sodium carbonate is the remaining amount after the initial weighing according to the stoichiometric ratio) were mixed. The homogeneously mixed material was incubated at 940°C in an air atmosphere for 8 hours, then allowed to cool naturally. It was then ground using a super micro stone disc mill with a disc spacing of 0.4 mm and a rotation speed of 3000 r / min to obtain a semi-finished product. Next, titanium dioxide was weighed and placed in a ball mill in a molar ratio of 1:0.007 with the above semi-finished product and titanium source (titanium element). The ball mill was run at a frequency of 48 Hz for 55 minutes. The homogeneously mixed material was incubated at 800°C in an air atmosphere for 6 hours, then allowed to cool naturally. Finally, it was ball milled and sieved to obtain pre-sodium-treated copper-zinc based sodium-ion battery cathode material A6.

[0068] For the sodium-ion battery cathode material A6 of this embodiment, the particle size, pH value, and sodium carbonate content in the free sodium were tested. Furthermore, A6 was manufactured into a button cell and cycle tests were performed. The cycle curve at 0.5C under conditions of 4.0 to 2.0V is shown in detail in Figure 1.

[0069] Comparative Example 1 The manufacturing method was the same as in Example 6, the only difference being that sodium carbonate did not need to be added during sanding in S1, and the entire amount of sodium carbonate weighed according to the stoichiometric ratio was added in step S3 to produce the pre-sodium-treated copper-zinc based sodium-ion battery cathode material D1.

[0070] For the sodium-ion battery cathode material D1 of this comparative example, the particle size, pH value, and sodium carbonate content in the free sodium were tested. Furthermore, D1 was manufactured into a button cell and cycle tests were performed. The cycle curve at 0.5C under conditions of 4.0 to 2.0V is shown in detail in Figure 1.

[0071] As can be seen from the above examples and comparative examples, the cathode material of Comparative Example 1 did not have sodium carbonate added during sanding, i.e., no pre-sodium treatment was performed. Although all were sintered, the lack of pre-sodium treatment prevented sodium ions on the material surface from sufficiently diffusing and moving into the material structure. As a result, the Na2CO3 content in the free sodium of the comparative example was 5.75%, which was much higher than the Na2CO3 content of Examples 1-6 (all within 3.5%). Furthermore, the retention rate of Comparative Example 1 at 4.0-2.0V 0.5C / 0.5C for 50 cycles was only 80.13%, which was much lower than the retention rate of Examples 1-6 at 4.0-2.0V 0.5C / 0.5C for 50 cycles. As can be seen by comparing Examples 1-6 with Comparative Example 1, by pre-sodium treatment, a portion of the sodium source is incorporated into the material structure beforehand, and then sintering is performed. This converts the sodium source inside the material structure into sodium ions, which diffuse and move sufficiently within the material structure, improving the material's cycle performance. At the same time, the amount of free sodium on the material surface is reduced, the reaction between the material and moisture and carbon dioxide in the air is reduced, improving the material's air stability, decreasing side reactions between the material and the electrolyte during the cycle process, and reducing the amount of cycle gas generated.

[0072] The applicant declares that while the above are merely specific embodiments of the present invention, the scope of protection of the present invention is not limited thereto, and that those skilled in the art should understand that any modifications or substitutions readily conceivable by those skilled in the art within the technical scope disclosed herein fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for producing a pre-sodium treated copper-zinc based sodium-ion battery cathode material, comprising the following steps: Sodium salts, zinc oxides, iron salts, manganese salts, nickel salts, and copper salts are weighed in equivalent amounts according to the stoichiometric ratios Na:Zn:Fe:Mn:Ni:Cu = 0.78:0.04:0.25 to 0.36:0.34:0.25:0.

04. S1: Wet pre-sodiumization: Add sodium salt, iron salt, manganese salt, nickel salt, and copper salt to a measuring cup, stir with water to dissolve, and obtain a mixed salt solution. Of this, add only 50% of the weighed weight of sodium salt; place zinc oxide and the mixed salt solution in a sand mill and sand for a certain period of time to obtain a mixture containing copper-zinc based elements. S2: The mixture containing the copper-zinc-based elements of S1 is spray-dried to obtain a precursor powder for the copper-zinc-based sodium-ion battery cathode material. S3: The precursor powder of S2 is mixed with the remaining sodium salt and sintered, an N source is added and coated, and finally pulverized to obtain a copper-zinc based sodium ion battery cathode material; the N source is one or more selected from Ca, Ti, Mg, Al, W, Zr, Sr, B, Ba, Ce, Mo, Co, La, Si, P, S, or Li. A method for producing a pre-sodium-treated copper-zinc based sodium-ion battery cathode material, characterized by containing the following:

2. A method for producing a pre-sodium-treated copper-zinc-based sodium-ion battery cathode material according to claim 1, characterized in that the zinc oxide is zinc oxide, the nickel salt and manganese salt are carbonate, sulfate, oxalate, or acetate, the iron salt is ferrous sulfate heptahydrate, ferrous sulfate monohydrate, ferrous oxalate, or ferrous chloride, the copper salt is anhydrous copper sulfate, and the zinc salt is anhydrous zinc sulfate, zinc sulfate monohydrate, or zinc sulfate heptahydrate.

3. The method for producing a pre-sodium-treated copper-zinc based sodium-ion battery cathode material according to claim 1, characterized in that the sanding is performed by weighing an equivalent amount of material:water:zirconium beads in a mass ratio of 1-1.5:3-5:2-5.

0.

4. A method for producing a pre-sodium-treated copper-zinc based sodium-ion battery cathode material according to claim 1, characterized in that in step S1, the sodium salt is sodium carbonate, sodium bicarbonate, sodium acetate, sodium nitrate, or sodium chloride.

5. A method for producing a pre-sodium-treated copper-zinc based sodium-ion battery cathode material according to claim 1, characterized in that the sintering is carried out in two stages, with the first sintering temperature being 870°C to 945°C and the second sintering temperature being 300°C to 800°C.

6. A method for producing a pre-sodium-treated copper-zinc based sodium-ion battery cathode material according to claim 1, characterized in that the coating is applied by a solid-phase method or a liquid-phase method.

7. The method for producing a pre-sodium-treated copper-zinc-based sodium-ion battery cathode material according to claim 1, characterized in that the grinding is performed by ball milling, mechanical grinding, or air-jet grinding, and the median particle size D50 of the copper-zinc-based sodium-ion battery cathode material after grinding is 5.2 to 14 μm.

8. The chemical formula of the copper-zinc based sodium ion battery cathode material is Na ｍ Cu ｘ Zn ｙ Fe ｚ M １－ｘ－ｙ－ｚ O ２ A method for producing a pre-sodium-treated copper-zinc-based sodium-ion battery cathode material according to claim 1, wherein 0.75 ≤ m ≤ 1.08, and M is one or more selected from Ni, Co, Mn, Ca, Ti, Mg, Al, W, Zr, Sr, B, Ba, Ce, Mo, La, Si, P, S, or Li, wherein 0.005 ≤ x ≤ 0.10, 0.005 ≤ y ≤ 0.09, and 0.20 ≤ z ≤ 0.45.

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