A method for preparing a sodium ion layered oxide cathode material coated

Abstract

The application discloses a kind of sodium ion layered oxide positive electrode material coating preparation method.The composition of the sodium ion layered oxide positive electrode material is loaded with 3,4-ethylenedioxythiophene polymer NaA x B y C z O2, the sodium ion oxide is prepared into nanoscale by ball milling method in the application, then sodium is removed by oxidizing agent, to avoid plugging the deintercalation channel of sodium ion, sodium source is embedded, to make up the irreversible sodium loss when forming electrolyte film, 3,4-ethylenedioxythiophene is added again, to form polymer with molecular structure, small energy gap and high conductivity, sodium is reinserted into part of sodium ion oxide with sodium loss and Na + Transport electron is deposited to polymer coating.The composite positive electrode material prepared in the application, Ni, Fe, Mn elements in core layer material present ladder distribution, on the one hand, through inhibiting harmful phase change, the structural stability of positive electrode material is improved, especially at high charge-discharge voltage, so that the capacity and cycle life of product are improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sodium ion battery materials, and particularly relates to a coating preparation method of a sodium ion layered oxide positive electrode material. BACKGROUND

[0002] With the development of society, the problems of energy shortage and environmental pollution caused by over-consumption of fossil energy are becoming increasingly serious, which seriously affects the sustainable development of human society. Therefore, it is an inevitable trend to vigorously develop renewable energy such as solar energy, wind energy, and tidal energy. However, renewable energy generation (such as wind energy and solar energy) is discontinuous and unstable, and it is difficult to be connected to the grid for use. Therefore, large-scale energy storage technology is a bottleneck technology for the popularization and application of renewable energy, and a low-cost, environmentally friendly energy storage material and technology are needed to provide continuous and stable energy output. Among many energy storage methods, lithium ion batteries are widely used in portable electronic devices and electric vehicles due to their high charge-discharge voltage, no memory effect, high energy density, small self-discharge, long service life, and other advantages. However, the lithium resource reserves are limited and unevenly distributed, which seriously limits its application in large-scale energy storage.

[0003] Sodium ion batteries are gradually becoming a research hotspot in the field of large-scale energy storage due to the abundance of sodium reserves (the abundance of Na in the earth's crust is 1000 times that of Li), uniform distribution, and low cost. However, the ionic radius of Na is larger than that of Li, and the atomic position will be different in similar structures, so the lithium ion battery positive electrode material cannot be directly used as the sodium ion battery positive electrode material. Therefore, finding suitable electrode materials for sodium ion batteries is the key to the practicality and industrialization of sodium ion batteries. Layered transition metal oxides have high reversible capacity, suitable operating voltage, and simple synthesis method, and are a very promising sodium ion battery positive electrode material. However, the complex phase transition during charging and discharging can easily cause the structure of the electrode material to collapse, and then cause the rapid capacity decay of the battery. The conductivity of this type of compound is poor, and carbon coating and doping methods are usually used, but this will reduce the volumetric energy density. Morphology control is one of the important means to enhance the structural stability of the material and improve the cycle performance of the battery.

[0004] Patent application No. CN110970612A discloses a transition metal oxide positive electrode material and its preparation and application. The composition of the positive electrode material is Na x A y B z O2. The Na x A y B zO2 is prepared by using metal oxide template-high temperature solid phase method, using metal oxide with special morphology as template, without introducing additional template, without removing template and other post-processing process, simple and easy. Na x A y B z O2 microspheres can relieve the mechanical stress generated in the process of sodium ion intercalation and deintercalation, reduce the contact area of active material and electrolyte, thereby improving the structural stability and cycle stability of the material. Na x A y B z O2 nanowires have shorter ion transport path, higher electrical conductivity and stronger strain adaptability, thus showing higher discharge capacity and cycle stability. The prepared Na x A y B z O2 microspheres and nanowires show high specific capacity and excellent rate performance and cycle performance through electrochemical performance test. However, the capacity and cycle life of the product are not ideal at high charge and discharge voltage. SUMMARY

[0005] In view of the deficiencies of the prior art, the purpose of the present application is to provide a coating preparation method of sodium ion layered oxide positive electrode material.

[0006] Firstly, the method relies on the inherent NaA x B y C z O2 oxidation capacity, rather than the oxidation capacity of the oxidizing agent on the outer surface as the driving force of the polymerization process. Therefore, there is no risk of leaching of residual oxidizing agent or oxidizing agent by-products from the polymer into the battery electrolyte, which will cause serious damage to the anode electrode process. Secondly, the polymerization reaction: re-inserting sodium into the partially desodiated NaA x B y C z O2 and Na + transport electrons are deposited to the polymer coating.

[0007] The technical scheme of the present application is as follows:

[0008] The present application provides a coating preparation method of sodium ion layered oxide positive electrode material, comprising the following steps:

[0009] (1) A, B and C with a molar mass ratio of x:y:z are weighed and configured into a solution, under inert gas, an alkaline solution is added for reaction, after reaction, filtration and drying, dry matter is obtained, and after grinding with sodium salt, sintering is carried out to obtain sodium ion oxide NaA x B y C z O2;

[0010] (2) oxidizing NaA x B y C z O2 is prepared into nanoscale by using a ball milling method;

[0011] (3) under inert gas, the prepared nanoscale sodium ion oxide NaA x B y C z O2 is dissolved in an organic solvent, a denauration is added to obtain a mixed solution;

[0012] (4) a sodium source and 3,4-ethylenedioxythiophene are added to the mixed solution in step (3) to obtain NaA x B y C z O2, that is, a sodium ion layered oxide positive electrode material;

[0013] wherein A is a transition metal, which is one of iron, copper, nickel, manganese and zinc; B is a transition metal, which is one of iron, copper, nickel, manganese and zinc, and B does not contain A; C is a transition metal, which is one of iron, copper, nickel, manganese and zinc, and C does not contain A and B; 0 < x ≤ 1, 0 < y ≤ 1, 0 < z ≤ 1, and x + y + z = 1.

[0014] The specific steps of step (2) are as follows: Na x A y B z O2 is placed in an organic solvent, stirred, and dried to obtain NaA x B y C z O2, and NaA x B y C z O2 is weighed in a ball mill at a ball-to-material mass ratio of 10:1, pre-milled at a speed of 300 rpm for 70 min, and then ball-milled at a speed of 400-1000 rpm for 60 min.

[0015] Specifically, the organic solvent in step (3) is acetonitrile or ethanol, and the oxidant is tetrafluoroboron nitric acid; the condition under inert gas is under argon gas with a water oxygen value of less than 0.01 ppm.

[0016] Preferably, the inert gas is argon, H2O < 1 ppm, and O2 < 1 ppm.

[0017] The sodium source in step (4) is sodium bis(trifluoromethanesulfonamide) (NaTFSI).

[0018] Bis-trifluoromethanesulfonamide sodium is a kind of stable salt under external environmental conditions, and TFSI is used as counterion to oxidize PEDOT to obtain polymer conductive material with high activity.

[0019] Preferably, in step (1), when the alkaline solution is added for reaction, the PH value of the reaction solution is maintained at 10.

[0020] In step (1), the specific steps of grinding and sintering the dry substance and sodium salt are as follows: the dry substance and sodium carbonate are mixed and ground at a molar mass ratio of 2:1.15, sintered in a muffle furnace at 550 DEG C for 4h, and then sintered at 900 DEG C for another 18h with temperature continuously rising.

[0021] The application also provides the sodium ion layered oxide positive electrode material prepared by the sodium ion layered oxide positive electrode material coating preparation method.

[0022] The application also provides a sodium ion battery positive electrode, which comprises the sodium ion layered oxide positive electrode material.

[0023] The application also provides a sodium ion battery, which comprises the sodium ion battery positive electrode.

[0024] The application has the following beneficial effects:

[0025] The preparation method of the application avoids the blockage of the deintercalation channel of sodium ions by preparing NaA x B y C z O2 into nanoscale, and then carrying out desodiation by using an oxidizing agent, embedding a sodium source to make up for the irreversible sodium loss when forming an electrolyte film, and adding 3,4-ethylenedioxythiophene to form a polymer with a molecular structure, a small energy gap and high conductivity, which is to reinsert sodium into part of the desodiated sodium ion oxide and transport electrons of Na + To the polymer coating.

[0026] The composite positive electrode material prepared by the application has a ladder distribution of Ni, Fe and Mn elements in the core layered material, which can improve the structural stability of the positive electrode material by inhibiting harmful phase change, especially at a high charge-discharge voltage, thereby improving the capacity and cycle life of the product. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 It is a structural schematic diagram for synthesizing PEDOT by oxidizing EDOT.

[0028] Figure 2 It is an XRD pattern of NaA x B y C z O2.

[0029] Figure 3 NaNi0.2Fe0.8O2 x B y C z TEM image of O2.

[0030] Figure 4 NaNi0.2Fe0.8O2 Figure 3 Enlarged area of box.

[0031] Figure 5 NaNi0.2Fe0.8O2 0.2 Fe 0.3 Mn 0.5 0.1C first cycle charge-discharge plot of O2.

[0032] Figure 6 NaNi0.2Fe0.8O2 0.2 Fe 0.3 Mn 0.5 Cycle performance plot of O2.

[0033] Figure 7 NaNi0.2Fe0.8O2 0.2 Fe 0.5 0.1C first cycle charge-discharge plot of Mn0.3O2.

[0034] Figure 8 NaNi0.2Fe0.8O2 0.2 Fe 0.5 Mn 0.3 Cycle performance plot of O2.

[0035] Figure 9 NaNi0.2Fe0.8O2 0.3 Fe 0.2 Mn 0.5 0.1C first cycle charge-discharge plot of O2.

[0036] Figure 10 NaNi0.2Fe0.8O2 0.3 Fe 0.2 Mn 0.5 Cycle performance plot of O2.

[0037] Figure 11 NaNi0.2Fe0.8O2 0.3 Fe 0.5 Mn 0.2 0.1C first cycle charge-discharge plot of O2.

[0038] Figure 12 NaNi0.2Fe0.8O2 0.3 Fe 0.5 Mn 0.2 Cycle performance plot of O2.

[0039] Figure 13 NaNi synthesized in Example 5 0.5 Fe 0.2 Mn 0.3 0.1C first cycle charge-discharge curve plot for O2.

[0040] Figure 14 NaNi synthesized in Example 5 0.5 Fe 0.2 Mn 0.3 Cycle performance plot for O2.

[0041] Figure 15 NaNi synthesized in Example 6 0.5 Fe 0.3 Mn 0.2 0.1C first cycle charge-discharge curve plot for O2.

[0042] Figure 16 NaNi synthesized in Example 6 0.5 Fe 0.3 Mn 0.2 Cycle performance plot for O2.

[0043] Figure 17 NaNi synthesized in Example 7 0.3 Fe 0.3 Mn 0.3 0.1C first cycle charge-discharge curve plot for O2.

[0044] Figure 18 NaNi synthesized in Example 7 0.3 Fe 0.3 Mn 0.3 Cycle performance plot for O2.

[0045] Figure 19 NaNi synthesized in Comparative Example 1 0.5 Fe 0.2 Mn 0.3 0.1C first cycle charge-discharge curve plot for O2.

[0046] Figure 20 NaNi synthesized in Comparative Example 1 0.5 Fe 0.2 Mn 0.3 Cycle performance plot for O2. DETAILED DESCRIPTION

[0047] Figure 1 Structure diagram of PEDOT synthesis process from oxidized EDOT. Figure 3 NaA loaded with PEDOT x B y C zTEM image of O2. Figure 4 For Figure 3 Enlarged area of the box. It can be seen that the elements of Ni, Fe and Mn in the core layer material present a ladder distribution.

[0048] NaA x B y C z Preparation process of O2.

[0049] Take ferrous sulfate, nickel sulfate, manganese sulfate, and the molar mass ratio x:y:z. Configure the above three kinds of soluble transition salt into a 2 mol / l solution, and configure sodium hydroxide into a 2 mol / l solution. At the same time, flow the salt solution and alkali solution into the reaction kettle, introduce argon, control the flow rate of the salt solution and alkali solution, keep the PH value in the bottom liquid at about 10, after the reaction is completed, take out the bottom liquid, filter, wash with deionized water, dry in a drying oven for 12 hours, then mix and grind with sodium carbonate according to the molar mass ratio 2:1.15, sinter in a muffle furnace at 550°C for four hours, continue to heat the temperature, sinter at 900°C for eighteen hours, and NaA x B y C z O2.

[0050] Figure 2 NaA x B y C z XRD pattern of O2.

[0051] Example 1

[0052] According to the preparation process of NaA x B y C z O2, take ferrous sulfate, nickel sulfate, and manganese sulfate, and the molar mass ratio 0.3:0.2:0.5. Configure the above three kinds of soluble transition salt into a 2 mol / l solution, and configure sodium hydroxide into a 2 mol / l solution. At the same time, flow the salt solution and alkali solution into the reaction kettle, introduce argon, control the flow rate of the salt solution and alkali solution, keep the PH value in the bottom liquid at about 10, after the reaction is completed, take out the bottom liquid, filter, wash with deionized water, dry in a drying oven for 12 hours, then mix and grind with sodium carbonate according to the molar mass ratio 2:1.15, sinter in a muffle furnace at 550°C for four hours, continue to heat the temperature, sinter at 900°C for eighteen hours, and NaNi 0.2 Fe 0.3 Mn 0.5 O2. Put NaNi 0.2 Fe 0.3 Mn 0.5 O2 in a planetary ball mill for dry grinding, and take NaNi 0.2 Fe0.3 Mn 0.5 O2, pre-milling in a ball mill at a speed of 300 rpm / min for 70 min, and then ball milling at a speed of 1000 rpm / min for 60 min to obtain nanoscale NaNi 0.2 Fe 0.3 Mn 0.5 O2, operating in an argon glove box under the condition that the water oxygen value is less than 0.01 ppm, weighing 10 g of NaNi 0.2 Fe 0.3 Mn 0.5 O2, placing in 200 ml of acetonitrile solution, and then adding 2 mol / L of tetrafluoroboron nitrate (NO2BF4) (tetrafluoroboron nitrate oxidizes part of the sodium in NaNi 0.2 Fe 0.3 Mn 0.5 O2), to obtain Na(1-m)Ni 0.2 Fe 0.3 Mn 0.5 O2, selecting Na(1-m)Ni 0.2 Fe 0.3 Mn 0.5 O2 potential of 3 V approaches NaNi 0.2 Fe 0.3 Mn 0.5 O2 redox potential. Adding 2 mol of sodium source bis-trifluoromethanesulfonamide sodium (NaTFSI), the 3,4-ethylenedioxythiophene (EDOT) polymerization reaction (generating the polymer PEDOT of EDOT) by reinsertion of the sodium source is oxidized without any other external source, and then adding EDOT to obtain NaNi loaded with PEDOT 0.2 Fe 0.3 Mn 0.5 O2.

[0053] Example 2

[0054] According to the preparation process of NaA x B y C z O2, weighing ferrous sulfate, nickel sulfate, and manganese sulfate with a molar mass ratio of 0.5:0.2:0.3, configuring the above three soluble transition salts into a 2 mol / l solution, configuring sodium hydroxide into a 2 mol / l solution, simultaneously flowing the salt solution and the alkali solution into the reaction kettle, introducing argon, and controlling the flow rate of the salt solution and the alkali solution to keep the PH value in the bottom liquid at about 10, after the reaction is completed, taking out the bottom liquid, filtering, washing with deionized water, drying in a drying oven for 12 hours, and then mixing and grinding with sodium carbonate at a molar mass ratio of 2:1.15, sintering in a muffle furnace at 550°C for four hours, continuing to heat the temperature, and sintering at 900°C for eighteen hours, to obtain NaNi0.2 Fe 0.5 Mn 0.3 O2. The NaNi 0.2 Fe 0.5 Mn 0.3 O2was placed in a planetary ball mill and dry ground with a ball-to-charge mass ratio of 10:1. The NaNi 0.2 Fe 0.5 Mn 0.3 O2was pre-milled in the ball mill at 300 rpm / min for 70 min and then ball-milled at 1000 rpm / min for 60 min. The nanoscale NaNi 0.2 Fe 0.5 Mn 0.3 O2was weighed in an argon glove box with a water and oxygen level below 0.01 ppm. 10 g of the NaNi 0.2 Fe 0.5 Mn 0.3 O2was placed in 200 ml of acetonitrile solution, and 2 mol / l of tetrafluoroboron nitrate (NO2BF4) was added (the tetrafluoroboron nitrate oxidizes part of the sodium in the NaNi 0.2 Fe 0.3 Mn 0.5 O2). Na(1-m)Ni 0.2 Fe 0.5 Mn 0.3 O2was selected 0.2 Fe 0.5 Mn 0.3 O2at a potential of 3 V approaches NaNi 0.2 Fe 0.5 Mn 0.3 O2redox potential. The addition of 2 mol of sodium source bis-trifluoromethanesulfonamide sodium (NaTFSI) allows the 3,4-ethylenedioxythiophene (EDOT) polymerization reaction (generation of the polymer PEDOT from EDOT) to proceed by reinsertion of the sodium source, oxidizing without any other external source, and then EDOT is added to obtain NaNi 0.2 Fe 0.5 Mn 0.3 O2.

[0055] Example 3

[0056] According to NaA x B y C zThe preparation process of O2 involves weighing ferrous sulfate, nickel sulfate, and manganese sulfate in a molar ratio of 0.2:0.3:0.5. A 2 mol / L solution of each of these three soluble transition salts is prepared, along with a 2 mol / L solution of sodium hydroxide. Simultaneously, the salt and alkali solutions are introduced into the reaction vessel, and argon gas is introduced while controlling the flow rates of the salt and alkali solutions to maintain the pH of the bottom solution at approximately 10. After the reaction is complete, the bottom solution is removed, filtered, washed with deionized water, and dried in a drying oven for 12 hours. It is then mixed with sodium carbonate in a molar ratio of 2:1.15 and ground. The mixture is sintered in a muffle furnace at 550°C for four hours, and then further heated to 900°C for eighteen hours to prepare NaNi. 0.3 Fe 0.2 Mn 0.5 O2. NaNi 0.3 Fe 0.2 Mn 0.5 O2 is dry-ground in a planetary ball mill, and NaNi is weighed out at a ball-to-material mass ratio of 10:1. 0.3 Fe 0.2 Mn 0.5 O2 was pre-milled in a ball mill at 300 rpm / min for 70 min, and then ball-milled at 1000 rpm / min for 60 min to obtain nano-sized NaNi. 0.3 Fe 0.2 Mn 0.5 O2, operated in an argon glove box under conditions where the water oxygen value is below 0.01 ppm, weigh 10 g of NaNi 0.3 Fe 0.2 Mn 0.5 O2 is placed in 200 ml of acetonitrile solution, and then 2 mol / L tetrafluoroborate nitric acid (NO2BF4) is added (tetrafluoroborate nitric acid is used to dissolve NaNi). 0.3 Fe 0.2 Mn 0.5 (partial oxidation of sodium in O2) yields Na(1-m)Ni 0.3 Fe 0.2 Mn 0.5 O2, choose Na(1-m)Ni 0.3 Fe 0.2 Mn 0.5 O2 potential is close to NaNi at 3V. 0.3 Fe 0.2 Mn 0.5 The redox potential of O2. Adding 2 mol of sodium bis(trifluoromethanesulfonamide) sodium (NaTFSI), the 3,4-ethylenedioxythiophene (EDOT) polymerization reaction (producing the EDOT polymer PEDOT) via sodium source reinsertion is oxidized without any other external source. Then, EDOT is added to obtain PEDOT-loaded NaNi. 0.3 Fe0.2 Mn 0.5 O2.

[0057] Example 4

[0058] According to NaA x B y C z O2, weigh ferrous sulfate, nickel sulfate, manganese sulfate, and the molar mass ratio is 0.5:0.3:0.2, configure the above three soluble transition salts into a 2 mol / l solution, configure sodium hydroxide into a 2 mol / l solution, flow the salt solution and the alkali solution into the reaction kettle at the same time, introduce argon, control the flow rate of the salt solution and the alkali solution, and keep the PH value in the bottom liquid at about 10, after the reaction is completed, take out the bottom liquid, filter, wash with deionized water, dry in a drying oven for 12 hours, then mix and grind with sodium carbonate according to the molar mass ratio of 2:1.15, sinter in a muffle furnace at 550°C for four hours, continue to heat the temperature, sinter at 900°C for eighteen hours, and NaNi 0.3 Fe 0.5 Mn 0.2 O2. Put NaNi 0.3 Fe 0.5 Mn 0.2 O2 in a planetary ball mill, weigh NaNi 0.3 Fe 0.5 Mn 0.2 O2, pre-mill in the ball mill at a speed of 300 rpm / min for 70 min, and then ball mill at a speed of 1000 pm / min for 60 min. Obtain nanoscale NaNi 0.3 Fe 0.5 Mn 0.2 O2, operate in an argon glove box under the condition that the water oxygen value is less than 0.01 ppm, weigh 10 g of NaNi 0.3 Fe 0.5 Mn 0.2 O2, put it in 200 ml of acetonitrile solution, and then add 2 mol / l tetrafluoroboron nitrate (NO2BF4) (tetrafluoroboron nitrate oxidizes part of the sodium in NaNi 0.3 Fe 0.5 Mn 0.2 O2), obtain Na(1-m)Ni 0.3 Fe 0.5 Mn 0.2 O2, select Na(1-m)Ni 0.3 Fe 0.5 Mn 0.2 O2 potential of 3V is close to NaNi 0.3 Fe 0.5 Mn 0.2O2. The redox potential of O2. The polymerization of 3,4-ethylenedioxythiophene (EDOT) (polymer of EDOT, PEDOT) by reinsertion of sodium source, with the addition of 2 mol sodium source bis-trifluoromethanesulfonamide sodium (NaTFSI), is oxidized without any other external source, and EDOT is added to it to obtain NaNi 0.3 Fe 0.5 Mn 0.2 O2.

[0059] Example 5

[0060] According to NaA x B y C z O2. The preparation process is as follows: weigh ferrous sulfate, nickel sulfate, and manganese sulfate in a molar mass ratio of 0.2:0.5:0.3, configure the above three soluble transition salts into a 2 mol / l solution, configure sodium hydroxide into a 2 mol / l solution, simultaneously flow the salt solution and the base solution into the reaction kettle, introduce argon gas, and control the flow rate of the salt solution and the base solution to keep the PH value in the bottom liquid at about 10. After the reaction is completed, the bottom liquid is taken out, filtered, washed with deionized water, and dried in a drying oven for 12 hours. Then, mix and grind with sodium carbonate in a molar mass ratio of 2:1.15, sinter in a muffle furnace at 550°C for four hours, continue to heat to 900°C, and sinter for eighteen hours to obtain NaNi 0.5 Fe 0.2 Mn 0.3 O2. Place NaNi 0.5 Fe 0.2 Mn 0.3 O2 in a planetary ball mill, weigh NaNi 0.5 Fe 0.2 Mn 0.3 O2, pre-mill in the ball mill at a speed of 300 rpm / min for 70 min, and then ball mill at a speed of 1000 pm / min for 60 min to obtain nanoscale NaNi 0.5 Fe 0.2 Mn 0.3 O2, operate in an argon glove box under the condition that the water oxygen value is less than 0.01 ppm, weigh 10 g of NaNi 0.5 Fe 0.2 Mn 0.3 O2 in 200 ml of acetonitrile solution, and then add 2 mol / l tetrafluoroboron nitrate (NO2BF4) (tetrafluoroboron nitrate oxidizes part of the sodium in NaNi 0.5 Fe 0.2 Mn 0.3 O2), to obtain Na(1-m)Ni 0.5 Fe 0.2Mn 0.3 O2, select Na(1-m)Ni 0.5 Fe 0.2 Mn 0.3 O2 potential 3V close to NaNi 0.5 Fe 0.2 Mn 0.3 O2 redox potential. Add 2 mol sodium source bis-trifluoromethanesulfonamide sodium (NaTFSI), 3,4-ethylenedioxythiophene (EDOT) polymerization (PEDOT is generated by EDOT) by sodium source reinsertion is oxidized without any other external source, and then add EDOT to obtain NaNi loaded with PEDOT 0.5 Fe 0.2 Mn 0.3 O2.

[0061] Example 6

[0062] According to NaA x B y C z O2 preparation process, weigh ferrous sulfate, nickel sulfate, manganese sulfate, molar mass ratio 0.3:0.5:0.2, configure the above three soluble transition salt into a 2 mol / l solution, configure sodium hydroxide into a 2 mol / l solution, at the same time flow into the salt solution and alkali solution into the reaction kettle, pass argon, and control the flow rate of the salt solution and alkali solution, keep the PH value in the bottom liquid at about 10, after the reaction is completed, take out the bottom liquid, filter, deionized water washing, dry in the drying oven for 12 hours, then mix and grind with sodium carbonate according to the molar mass ratio 2:1.15, sinter in the muffle furnace at 550℃ for four hours, continue to heat up, sinter at 900℃ for eighteen hours, NaNi can be prepared 0.5 Fe 0.3 Mn 0.2 O2. Put NaNi 0.5 Fe 0.3 Mn 0.2 O2 in the planetary ball mill for dry grinding, NaNi 0.5 Fe 0.3 Mn 0.2 O2, pre-grind in the ball mill at 300 rpm / min for 70 min, and then ball mill at 1000 pm / min for 60 min. Get nanoscale NaNi 0.5 Fe 0.3 Mn 0.2 O2, under the condition that the water oxygen value is less than 0.01 ppm, operate in the argon glove box, weigh 10g NaNi 0.5 Fe 0.3 Mn 0.2O2 was placed in 200 ml acetonitrile solution, and 2 mol / l tetrafluoroboron nitrate (NO2BF4) (tetrafluoroboron nitrate will oxidize NaNi 0.5 Fe 0.3 Mn 0.2 O2 (part of sodium oxidation in O2), to obtain Na(1-m)Ni 0.5 Fe 0.3 Mn 0.2 O2, select Na(1-m)Ni 0.5 Fe 0.3 Mn 0.2 O2, close to NaNi 0.5 Fe 0.3 Mn 0.2 O2 redox potential. Add 2 mol sodium source bis-trifluoromethanesulfonamide sodium (NaTFSI), 3,4-ethylenedioxythiophene (EDOT) polymerization (generate EDOT polymer PEDOT) by sodium source reinsertion Oxidation without any other external source, and then add EDOT to obtain NaNi loaded with PEDOT 0.5 Fe 0.3 Mn 0.2 O2.

[0063] Example 7

[0064] According to the preparation process of NaA x B y C z O2, weigh ferrous sulfate, nickel sulfate, manganese sulfate, and the molar mass ratio is 1 / 3:1 / 3:1 / 3, configure the above three soluble transition salts into a 2 mol / l solution, configure sodium hydroxide into a 2 mol / l solution, while flowing into the salt solution and alkali solution into the reactor, pass argon, and control the flow rate of the salt solution and alkali solution, keep the PH value in the bottom liquid at about 10, after the reaction is completed, take out the bottom liquid, filter, deionized water washing, dry in a drying oven for 12 hours, then mix and grind with sodium carbonate according to the molar mass ratio of 2:1.15, sinter in a muffle furnace at 550°C for four hours, continue to heat the temperature to 900°C, sinter for eighteen hours, to obtain NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2. NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 was placed in a planetary ball mill for dry grinding, and NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3O2, pre-milling in a ball mill at 300 rpm / min for 70 min, and then ball milling at 1000 rpm / min for 60 min. The nanoscale NaNi 0.3 Fe 0.3 Mn 0.3 O2, under the condition that the water oxygen value is less than 0.01 ppm, 10 g of NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, is placed in 200 ml of acetonitrile solution, and then 2 mol / l of tetrafluoroboron nitrate (NO2BF4) (tetrafluoroboron nitrate oxidizes part of the sodium in NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, to obtain Na(1-m)Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, select Na(1-m)Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, when the potential is 3 V, it is close to NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, the redox potential. By adding 2 mol of sodium source bis-trifluoromethanesulfonamide sodium (NaTFSI), the 3,4-ethylenedioxythiophene (EDOT) polymerization reaction (PEDOT is generated by EDOT) by reinsertion of the sodium source is oxidized without any other external source, and then EDOT is added to obtain NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2.

[0065] Comparative Example 1

[0066] Ferrous sulfate, nickel sulfate, and manganese sulfate are weighed, and the molar mass ratio is 0.5:0.2:0.3. A solution of 2 mol / l of the above three soluble transition salts is prepared, and a solution of 2 mol / l of sodium hydroxide is prepared. At the same time, the salt solution and the base solution are flowed into the reaction kettle, argon is introduced, and the flow rate of the salt solution and the base solution is controlled to keep the PH value in the bottom liquid at about 10. After the reaction is completed, the bottom liquid is taken out, filtered, washed with deionized water, and dried in a drying oven for 12 hours. Then, it is mixed and ground with sodium carbonate at a molar mass ratio of 2:1.15, sintered in a muffle furnace at 550°C for four hours, and then the temperature is continuously increased to 900°C for eighteen hours. NaNi 0.5 Fe 0.2 Mn 0.3 O2. NaNi 0.5 Fe 0.2 Mn0.3 O2was placed in a planetary ball mill and dry ground, the ball-to-material mass ratio was 10:1 0.5 Fe 0.2 Mn 0.3 O2, pre-milling in a ball mill at 300 rpm / min for 70 min, and then ball milling at 1000 rpm / min for 60 min. The nanoscale NaNi 0.5 Fe 0.2 Mn 0.3 O2.

[0067] Test Example 1

[0068] The active material prepared in Example 1-7 and the conductive agent material, binder were mixed, stirred uniformly, the ratio of active material, conductive agent, binder was 8:1:1, the mixed slurry was uniformly coated on the aluminum foil current collector, dried in a drying oven at 100°C for 10 hours, and the aluminum foil coated with slurry was punched into small round pieces by a punch machine.

[0069] The active material prepared in Comparative Example 1 and the conductive agent material, binder were mixed, stirred uniformly, the ratio of active material, conductive agent, binder was 8:1:1, the mixed slurry was uniformly coated on the aluminum foil current collector, dried in a drying oven at 100°C for 10 hours, and the aluminum foil coated with slurry was punched into small round pieces by a punch machine.

[0070] The electrode material was used as the working electrode, a metal sodium sheet was used as the counter electrode, 1M NaCLO4 EC / DEC (vol, 1:1) was used as the electrolyte, a 2016 button cell was assembled in an argon glove box with a water oxygen value below 0.01 ppm, and the button cell was tested by constant current charge and discharge mode, and the test voltage window was 2V-4V. The test results are shown in Figures 5-20 The specific results are shown in Table 1.

[0071] Table 1

[0072]

[0073]

[0074] As can be seen from Table 1, the positive electrode material prepared by the composite preparation method of the present application can improve the cycle performance of the sodium ion battery positive electrode material, and these materials exhibit excellent chemical properties.

Claims

1. A method for coating sodium-ion layered-oxide cathode material, characterized in that, The method comprises the following steps: (1) A, B, C with molar mass ratio of x:y:z are respectively weighed and configured into a solution, under inert gas, a basic solution is added for reaction, the pH value of the reaction solution is kept at 10, after reaction, filtration and drying are carried out, dry matter is obtained, the dry matter is mixed and ground with sodium carbonate at a molar mass ratio of 2:1.15, sintering is carried out in a muffle furnace at 550 DEG C for 4h, the temperature continues to rise, sintering is carried out at 900 DEG C for 18h, and sodium ion oxide NaA is obtained x B y C z O2; (2) Sodium ion oxide NaA x B y C z O2 is prepared into nanoscale using a ball milling method; (3) Under inert gas, the prepared nanometer sodium ion oxide NaA x B y C z O2 is dissolved in an organic solvent, and tetrafluoroboron nitric acid is added for desodiation to obtain a mixed solution; (4) adding sodium bis-trifluoromethanesulfonamide and 3,4- ethylenedioxythiophene to the mixed solution in step (3) to obtain NaA x B y C z O2, i.e., sodium-ion layered-oxide positive electrode material; Wherein, A is a transition metal, which is one of iron, copper, nickel, manganese and zinc; B is a transition metal, which is one of iron, copper, nickel, manganese and zinc, and B does not contain A; C is a transition metal, which is one of iron, copper, nickel, manganese and zinc, and C does not contain A and B; 0 The NaA x B y C z O2 potential is 3V, and NaA x B y C z The transition metal elements in O2 are in a ladder distribution.

2. The method for preparing sodium ion layered oxide cathode material coating as described in claim 1, characterized in that, The specific step of step (2) is: taking NaA and Na2CO3 according to the mass ratio of 10:1 x B y C z O2, and pre-milling in a ball mill at a speed of 300 rpm for 70 min, and then ball milling at a speed of 400-1000 rpm for 60 min.

3. The method for preparing sodium ion layered oxide cathode material coating as described in claim 1, characterized in that, The organic solvent in step (3) is acetonitrile or ethanol; the condition under inert gas is under the condition of argon with water oxygen value lower than 0.01 ppm.

4. The method for preparing sodium ion layered oxide cathode material coating as described in claim 1, characterized in that, In step (1), the alkaline solution is sodium hydroxide solution.

5. The sodium-ion layered oxide cathode material prepared by the sodium-ion layered oxide cathode material coating preparation method according to any one of claims 1-4.

6. A sodium-ion battery cathode, characterized in that, The sodium-ion battery cathode comprises the sodium-ion layered oxide cathode material according to claim 5.

7. A sodium-ion battery, characterized in that, The sodium-ion battery comprises the sodium-ion battery cathode according to claim 6.

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