Modification method of spinel nickel sodium manganate positive electrode material

Abstract

A modification method of a spinel sodium nickel manganese oxide positive electrode material belongs to the technical field of sodium ion battery positive electrode material production, and comprises the following steps: fumigating the spinel sodium nickel manganese oxide positive electrode material in acid steam, washing the fumigated spinel sodium nickel manganese oxide positive electrode material with deionized water, drying, and calcining to obtain the spinel sodium nickel manganese oxide positive electrode material. The modified spinel nickel sodium manganate positive electrode material is obtained; the structural formula of the spinel sodium nickel manganese oxide positive electrode material is NaNi < 0.5 > Mn < 1.5 > O < 4 >. According to the method, two important processes are provided during acid treatment of fumigation through acid steam, firstly, an H < + > / Na < + > exchange reaction improves the oxidation-reduction capacity of the material, and formation of a sodium channel is accelerated; and secondly, Na2O in the component Na2MnO3 of the spinel sodium nickel manganese oxide positive electrode material can be filtered out to form MnO2, sodium can be embedded into the MnO2 in the discharge process, and the embedded amount of Na is increased, so that the performance of the material is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of production of positive electrode materials for sodium ion batteries, and specifically relates to a method for modifying spinel sodium nickel manganate positive electrode materials. Background Art

[0002] As a highly efficient energy storage device, sodium-ion batteries can convert electrical energy into chemical energy for use in various fields. In recent years, based on the demand for higher-specification energy storage devices in the field of new energy electric vehicles, the development of sodium-ion batteries in the direction of high specific energy, high power density, high safety, long cycle life, and low cost has become increasingly urgent. The performance of the positive electrode material will directly affect the battery's charge and discharge capacity, cycle performance, rate performance, and high-temperature thermal stability. The spinel sodium nickel manganese oxide positive electrode material has a very high discharge platform and a high energy density, which has quickly become a research focus in the field of energy and materials.

[0003] Spinel nickel sodium manganese oxide cathode material is considered to be one of the promising cathode materials to break through the current bottleneck of sodium ion battery application due to its low cost, good safety and high energy density. However, spinel nickel sodium manganese oxide cathode material itself also has some serious problems, such as poor cycle performance, too fast voltage decay, too high first irreversible capacity, etc., which seriously hinder its commercial application process. Summary of the invention

[0004] In view of the above problems existing in spinel sodium nickel manganese oxide positive electrode materials, the present invention provides a method for modifying spinel sodium nickel manganese oxide positive electrode materials treated with acid vapor.

[0005] The technical scheme of the present invention is: placing the spinel sodium nickel manganate positive electrode material in acid vapor for fumigation, then washing the fumigated spinel sodium nickel manganate positive electrode material with deionized water, drying and calcining, to obtain a modified spinel sodium nickel manganate positive electrode material; the structural formula of the modified spinel sodium nickel manganate positive electrode material is: NaNi 0.5 Mn 1.5 O4.

[0006] The acid treatment of the present invention by acid vapor fumigation has two important processes: first, H + / Na + The exchange reaction improves the redox ability of the material and accelerates the formation of sodium channels. Secondly, Na2O in the Na2MnO3 component of the spinel sodium nickel manganese oxide positive electrode material can be filtered out to form MnO2, and MnO2 can embed sodium during the discharge process, increasing the amount of Na embedded, thereby improving the performance of the material.

[0007] The acid treatment that has been studied is to acid immerse the material, which will cause a certain degree of corrosion to the surface of the material. Although it can reduce the loss of capacity, it has an adverse effect on its cycle performance.

[0008] The present invention adopts a simple process flow and uses acid vapor to form an acidic atmosphere to carry out acid treatment on the spinel sodium nickel manganese oxide positive electrode material. Compared with the acid immersion treatment, it is much milder and can effectively avoid the damage of the acid solution to the surface of the material. While improving its first irreversible capacity, it also enhances the cycle performance of the modified material, thereby better improving the performance of the spinel sodium nickel manganese oxide positive electrode material.

[0009] Furthermore, the concentration of the acid vapor in the present invention is 1-2 mol / L.

[0010] The acid is at least any one of hydrochloric acid, nitric acid, oxalic acid or acetic acid.

[0011] Acid vapor treatment mainly uses acidic atmosphere to treat the surface of materials. + With the material surface Na + Conduct H + / Na + The exchange reaction removes the residual Na2O on the surface of the spinel sodium nickel manganese oxide positive electrode material, inhibits the side reaction between the electrode and the electrolyte, and thus improves the electrochemical performance of the material. In the concentration range of 1 to 5 mol / L, an appropriate acid vapor atmosphere can be obtained to treat the surface of the material.

[0012] The fumigation time is 5 to 24 hours, more preferably, the fumigation time is 12 hours. The acid vapor treatment is relatively mild, and the spinel nickel sodium manganese oxide positive electrode material needs to be treated in the acid atmosphere for a sufficient time to undergo H + / Na + The exchange reaction is more complete within this time range.

[0013] In order to completely remove the moisture left in the positive electrode material due to the acid vapor treatment, the calcination temperature environment is 300°C and the calcination time is 3h. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is the SEM image of the original spinel sodium nickel manganese oxide positive electrode material without acid treatment.

[0015] Figure 2 This is the SEM image of the material treated with acetic acid vapor. DETAILED DESCRIPTION

[0016] 1. Preparation of spinel sodium nickel manganese oxide positive electrode material: The spinel sodium nickel manganate precursor is prepared by coprecipitation method, with sulfate as the metal salt solution, sodium carbonate as the precipitant, ammonia water as the complexing agent, and a certain injection speed and pH value are controlled. The coprecipitation reaction is carried out under 60°C water bath heating to obtain the spinel sodium nickel manganate precursor suspension. After sedimentation, washing and drying, the spinel sodium nickel manganate precursor is obtained.

[0017] The prepared spinel sodium nickel manganate precursor was uniformly mixed with sodium salt and then calcined. During calcination, the temperature was first raised to 500°C, kept warm for 3 hours, then raised to 900°C, kept warm for 8 hours, and finally cooled to room temperature to obtain the desired spinel sodium nickel manganate positive electrode material, whose chemical formula is Na 0.5 Mn 1.5 Ni 0.5 O4.

[0018] 2. Modification process: Implementation 1: Measure a certain amount of acetic acid, add deionized water to dilute, and obtain an acetic acid aqueous solution with a concentration of 2 mol / L. Pour the above acetic acid aqueous solution into a container, hang a funnel-shaped filter paper at the mouth of the container, and then evenly distribute the spinel nickel sodium manganese oxide positive electrode material on the filter paper, and cover the opening above the filter paper with a glass sheet to prevent acid vapor from escaping or liquefying and dripping into the material.

[0019] The container was then placed in a constant temperature water bath at 40-60°C, and the acetic acid aqueous solution in the container was stirred magnetically to form acid vapor, and samples were taken after fumigation for 12 hours.

[0020] The sample was washed with deionized water for 2 to 3 times, filtered, and then placed in an electric hot air drying oven at 70°C for 2 hours to obtain a dried material. The dried material was calcined in a muffle furnace at 300°C for 3 hours to remove the moisture left in the material and obtain a modified material sample.

[0021] Implementation 2: Measure a certain amount of hydrochloric acid, add deionized water to dilute, and obtain a hydrochloric acid aqueous solution with a concentration of 2 mol / L. Pour the above hydrochloric acid aqueous solution into a container, hang a funnel-shaped filter paper at the mouth of the container, and then evenly distribute the positive electrode material on the filter paper, and cover the opening above the filter paper with a glass sheet to prevent the acid vapor from escaping or liquefying and dripping into the material.

[0022] The container was then placed in a constant temperature water bath at 40-60°C, and the hydrochloric acid aqueous solution in the container was stirred magnetically to form acid vapor, and samples were taken after fumigation for 12 hours.

[0023] The sample was washed with deionized water for 2 to 3 times, filtered, and then placed in an electric hot air drying oven at 70°C for 2 hours to obtain a dried material. The dried material was calcined in a muffle furnace at 300°C for 3 hours to remove the moisture left in the material and obtain a modified material sample.

[0024] Comparative Example: The spinel sodium nickel manganese oxide positive electrode material prepared in the first step is used without acid treatment.

[0025] 4. Test: Assembled button cells were used to conduct parallel tests on the charge and discharge performance of the modified material samples.

[0026] The sample, binder and conductive agent were mixed evenly in a mass ratio of 8:1:1, and an appropriate amount of 1-methyl-2-pyrrolidone was added to make a slurry, which was evenly coated on the aluminum foil with a thickness of about 5 mg / cm 3 , put it in the oven for drying, and then punch it out to make the positive electrode.

[0027] Using a sodium sheet as the negative electrode, the battery was assembled in a glove box filled with argon.

[0028] V. Performance Analysis: 1. SEM analysis Depend on Figure 1 , 2 It can be seen that the morphology of both materials is spherical particles, and no obvious corrosive holes appear on the surface of the materials after being treated with acetic acid, indicating that the treatment method is gentle enough and will not damage the basic structure of the material.

[0029] 2. Electrochemical performance test The modified material obtained by the method of the present invention is used to assemble a battery to test the initial charge and discharge performance of the material at 0.05C, and the cycle performance test is carried out at 0.5C.

[0030] The first discharge capacity of the material without acid treatment in the comparative example is 125mAh / g, and the charge-discharge efficiency is 79%; the first discharge capacity of the material treated with acetic acid vapor and the material treated with hydrochloric acid vapor in implementation one and implementation two are 131Ah / g and 127Ah / g, respectively, and the charge-discharge efficiency is about 83% and 85%, respectively. The first discharge efficiency of the material without acid treatment is significantly lower than that of the material treated with acid, so acid treatment can improve the first charge-discharge efficiency of the material.

Claims

1. A method for modifying a spinel sodium nickel manganese oxide positive electrode material, characterized in that: The spinel sodium nickel manganese oxide positive electrode material is placed in acid vapor for fumigation, and then the fumigated spinel sodium nickel manganese oxide positive electrode material is washed with deionized water, dried, and calcined to obtain a modified spinel sodium nickel manganese oxide positive electrode material.

2. The method for modifying the spinel sodium nickel manganese oxide positive electrode material according to claim 1, characterized in that: The structural formula of the modified spinel sodium nickel manganese oxide positive electrode material is: NaNi 0.5 Mn 1.5 O4.

3. The method for modifying the spinel sodium nickel manganese oxide positive electrode material according to claim 1, characterized in that: The concentration of the acid vapor is 1-2 mol / L.

4. The method for modifying the spinel sodium nickel manganese oxide positive electrode material according to claim 1, characterized in that: The acid is at least any one of hydrochloric acid, nitric acid, oxalic acid or acetic acid.

5. The method for modifying the spinel sodium nickel manganese oxide positive electrode material according to claim 1, characterized in that: The fumigation time is 5 to 24 hours.

6. The method for modifying the spinel sodium nickel manganese oxide positive electrode material according to claim 5, characterized in that: The fumigation time is 12 hours.

7. The method for modifying the spinel sodium nickel manganese oxide positive electrode material according to claim 1, 2, 3, 4 or 5, characterized in that: The calcination temperature environment is 300°C and the calcination time is 3h.

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