A method for preparing a copper element-doped nickel-iron-manganese precursor material and a sodium battery positive electrode material thereof

Abstract

This invention discloses a method for preparing copper-doped nickel-iron-manganese precursor materials and their corresponding sodium-ion battery cathode materials. By pre-adding a specific amount of complexing agent to a mixed metal salt solution to create a micro-complexed solution, the concentration of free metal ions is reduced to a certain extent, slowing down the release rate of metal ions and reducing the possibility of rapid hydroxide formation and oxidation, thus improving the stability of the preparation process. When copper ions are used for doping, the incompatibility problem of copper hydroxide can also be solved. In other words, this invention, through optimized complexation processes combined with special anti-oxidation measures, prepares multi-component precursor materials with uniform phase, uniform particle size, and excellent morphology, as well as corresponding sodium-ion battery cathode materials. Furthermore, this invention has the advantages of a short preparation process, low cost, and simple operation.

Description

Technical Field

[0001] This invention relates to the preparation of battery electrode materials, specifically to a method for preparing copper-doped nickel-iron-manganese precursor materials and their sodium battery cathode materials, belonging to the field of sodium battery electrode material preparation technology. Background Technology

[0002] In recent years, lithium-ion batteries have been favored by the market due to their high energy density. However, with the widespread use of clean energy, the demand for energy storage batteries is increasing, and the problems of high cost and scarce lithium resources are becoming more and more apparent. The global lithium resource shortage restricts the sustainable development of lithium batteries. Research has found that sodium-ion batteries have a similar working principle to lithium-ion batteries, and compared with lithium-ion batteries, sodium-ion batteries have advantages such as abundant raw materials, low production cost, high energy density, high voltage platform, and excellent overall performance. Domestic and foreign scholars generally agree that it is the most promising ideal capacitor to replace lithium-ion batteries. Nickel-iron-manganese ternary cathode material, as a low-cost positive valence material for sodium-ion batteries, is based on the classic sodium-ion cathode material NaNi. 0.5 Mn 0.5 Derived from the O2 system, it reduces interlayer spacing by introducing low-cost iron ions, offering advantages such as inhibiting solvent co-intercalation, enhancing cycling stability, and lower cost and environmental friendliness. However, due to Na... + Continuous transition metal sliding and Na during the insertion / extraction process + Vacancy ordering, layered transition metal oxide Na x MO2 materials undergo a crystal phase transition accompanied by significant changes in unit cell volume. These changes can cause structural collapse in the cathode material, reducing its recyclability. While heterogeneous ion substitution with electrochemically inactive cations can improve cycle performance, the incorporation of inactive elements leads to a decrease in specific capacity. Currently, the co-precipitation method for preparing copper-doped precursors is prone to copper phase separation, where copper hydroxide and nickel-iron-manganese hydroxide are incompatible, resulting in larger lattice defects, poor morphology, and more impurities in the product.

[0003] Furthermore, the study found that the preparation of undoped nickel-iron-manganese layered hydroxides (type 111) mainly employs a liquid-phase coprecipitation method. However, due to the significant differences in the solubility products of the three ions (nickel, iron, and manganese), coprecipitation is difficult. Therefore, a complexing agent must be added during the reaction to reduce the concentration of free nickel and manganese ions in the solution, making them similar to the concentration of free iron ions, thereby ensuring the coprecipitation of the three ions. And because Fe... 2+ It is easily oxidized by air to Fe 3+ Fe 3+The pH of the precipitate is very low, so it must be prevented by adding antioxidants and maintaining an inert atmosphere. The preparation effect of the ternary hydroxide will seriously affect the electrochemical performance of the subsequently synthesized sodium-containing ternary oxide precursor. During the preparation process, the reaction conditions, including the type of precipitant, the concentration of the complexing agent, and the stirring speed, will all affect the precipitation effect, including the particle size, tap density, and microstructure of the precipitate. Currently, the main method for preparing this type of ternary precursor on the market is as follows: 1. First, prepare a base solution with a certain ammonia concentration and pH, and add antioxidants and introduce nitrogen gas into it. The antioxidants used are mostly sodium sulfite and sodium thiosulfate; 2. Then, add the prepared mixed metal salt solution and the alkaline solution containing the complex to the reactor dropwise; 3. After a period of reaction by setting the stirring speed and temperature of the reactor, the ternary precursor is obtained. The production method of this type of ternary hydroxide is relatively cumbersome, and the uniformity of the obtained samples is insufficient, and the product morphology needs to be improved. The drawbacks of this process are: 1) Since sodium sulfite and sodium thiosulfate are strong base-weak acid salts, their alkalinity in water can affect the pH control during precipitation. Furthermore, excessive addition of sulfite can lead to a large amount of sodium sulfate in the initial product, increasing the difficulty of subsequent impurity removal. 2) This process has a long cycle, including nucleation, passivation, and growth phases, resulting in higher production costs. 3) The product prepared by this process has poor particle size uniformity, containing many fine crystals. This leads to agglomeration and caking after drying. Summary of the Invention

[0004] To address the problems of long preparation cycles and poor product uniformity in existing sodium-ion battery cathode material precursors, this invention provides a method for preparing copper-doped nickel-iron-manganese precursor materials and a corresponding method for preparing sodium-ion battery cathode materials. By optimizing the complexation process and combining it with special anti-oxidation measures, a multi-component precursor material with uniform phase, uniform particle size, and excellent morphology, as well as its corresponding sodium-ion battery cathode material, can be prepared. It also has the advantages of a short preparation process, low cost, and simple operation.

[0005] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0006] According to a first embodiment of the present invention, a method for preparing a sodium battery cathode material is provided:

[0007] A method for preparing copper-doped nickel-iron-manganese precursor materials, the method comprising:

[0008] 1) First, add deoxygenated water, antioxidant, precipitant and dispersant to the reaction vessel and start stirring. Then, introduce protective gas and heat. Finally, add complexing agent and mix evenly to obtain the reaction base liquid.

[0009] 2) Mix copper salt solution, nickel salt solution, ferrous salt solution and manganese salt solution to obtain a mixed metal salt solution, and then add a complexing agent to the mixed metal salt solution to obtain a micro-complexed mixed metal salt solution.

[0010] 3) Add the micro-complexed mixed metal salt solution obtained in step 2) to the reaction substrate in step 1) to carry out the reaction.

[0011] 4) After the reaction in step 3) has proceeded for a period of time, the coarse particulate product in the reaction system is separated and aged. After aging, the product is then filtered, washed, and dried to obtain the copper-doped nickel-iron-manganese precursor material.

[0012] Preferably, in step 1), the antioxidant is one or more of methyl gallate, ethyl gallate, propyl gallate, isopropyl gallate, butyl gallate, tert-butyl gallate, and gallic acid.

[0013] Preferably, in step 1), the amount of antioxidant added is such that its system concentration is not greater than 0.05 mol / L, preferably 0.02 to 0.045 mol / L.

[0014] Preferably, in step 1), the precipitant is an alkali, preferably sodium hydroxide.

[0015] Preferably, in step 1), the amount of precipitant added is such that the pH of the system is 9 to 13, preferably 10 to 12 (the concentration of the precipitant is about 0.4 to 0.6 mol / L).

[0016] Preferably, in step 1), the dispersant is polyethylene glycol and / or polyvinyl alcohol, preferably polyethylene glycol and / or polyvinyl alcohol with an average molecular weight of 800 to 8000, more preferably one or more of polyethylene glycol (1000), polyethylene glycol (1500), polyethylene glycol (2000), polyethylene glycol (4000), polyethylene glycol (6000), polyvinyl alcohol (1788), and polyvinyl alcohol (2488).

[0017] It should be noted that the values ​​in parentheses represent the average molecular weight of the polymer. For example, polyethylene glycol (1000) indicates polyethylene glycol with an average molecular weight of approximately 1000. These substances are all commercially available. For instance, polyethylene glycol (1000), polyethylene glycol (1500), polyethylene glycol (2000), polyethylene glycol (4000), and polyethylene glycol (6000) can be purchased from Shanghai Donghui Chemical Technology Co., Ltd., Nantong Hesai New Materials Co., Ltd., or Jiangsu Haian Petrochemical Plant, etc. Polyvinyl alcohol (1788) and polyvinyl alcohol (2488) can be purchased from Jinan Hongke Chemical Technology Co., Ltd., Zhengzhou Jiajie Chemical Products Co., Ltd., or Henan Chuangxiang Chemical Products Co., Ltd., etc.

[0018] Preferably, in step 1), the amount of dispersant added is such that the system concentration is not greater than 0.05 mol / L, preferably 0.02 to 0.04 mol / L.

[0019] Preferably, in step 1), the complexing agent is one or more of ammonia, citric acid, oxalic acid, and tartaric acid.

[0020] Preferably, in step 1), the amount of complexing agent added is such that its system concentration is not greater than 1 mol / L, preferably 0.3 to 0.8 mol / L.

[0021] Preferably, in step 1), the protective gas is an inert gas and / or nitrogen, with nitrogen being the most preferred. The flow rate of the protective gas is not less than 80 mL / min, and preferably 90–150 mL / min.

[0022] Preferably, in step 1), the stirring rate is not less than 100 rpm, and more preferably 200 to 600 rpm.

[0023] Preferably, in step 1), the heating is to heat the system to 40-70°C, more preferably 45-65°C.

[0024] Preferably, in step 2), the copper salt is one or more of copper sulfate, copper nitrate, and copper chloride. The nickel salt is one or more of nickel sulfate, nickel nitrate, and nickel chloride. The ferrous salt is one or more of ferrous sulfate, ferrous nitrate, and ferrous chloride. The manganese salt is one or more of manganese sulfate, manganese nitrate, and manganese chloride. Preferably, the molar ratio of nickel ions, copper ions, manganese ions, and ferrous ions in the mixed metal salt solution is (1-x):x:0.8~1.2:0.8~1.2, where 0≤x≤0.3.

[0025] It should be noted that, in the preferred embodiment of this invention, for example, when the molar ratio of nickel ions, copper ions, manganese ions, and ferrous ions is (1-x):x:0.8~1.2:0.8~1.2, if the amount of copper salt added is x=0, then an undoped type 111 nickel-iron-manganese precursor material is prepared, and the corresponding type 111 sodium battery cathode material is obtained by further preparation. In this invention, the metal salts used in the precipitation process are mainly their hydrates. For example, nickel sulfate salts include anhydrous nickel sulfate and hydrated nickel sulfate, and other metal salts also include anhydrous salts and hydrated salts.

[0026] Preferably, in the micro-complexed mixed metal salt solution, the concentration of the complexing agent is ≤0.03 mol / L, and more preferably 0.015~0.025 mol / L.

[0027] Preferably, in step 3), the amount of the micro-complexed mixed metal salt solution added is such that the concentration of the mixed metal salt in the reaction system is 0.2 to 0.5 mol / L, preferably 0.25 to 0.45 mol / L.

[0028] Preferably, in step 3), the reaction time is not less than 1 hour, and more preferably 3 to 12 hours.

[0029] Preferably, in step 4), the separation is cyclone separation. The particle size range of the coarse product is not less than 10 micrometers.

[0030] In this invention, the molecular formula of the copper-doped nickel-iron-manganese precursor material can be represented as: Ni 1 / 3- x Cu x Fe 1 / 3 Mn 1 / 3 (OH)2·0.5H2O, where 0≤x≤0.3.

[0031] According to a second embodiment of the present invention, a method for preparing a sodium battery cathode material is provided:

[0032] A method for preparing a sodium battery cathode material, the method comprising:

[0033] 1) First, add deoxygenated water, antioxidant, precipitant and dispersant to the reaction vessel and start stirring. Then, introduce protective gas and heat. Finally, add complexing agent and mix evenly to obtain the reaction base liquid.

[0034] 2) Mix copper salt solution, nickel salt solution, ferrous salt solution and manganese salt solution to obtain a mixed metal salt solution, and then add a complexing agent to the mixed metal salt solution to obtain a micro-complexed mixed metal salt solution.

[0035] 3) Add the micro-complexed mixed metal salt solution obtained in step 2) to the reaction substrate in step 1) to carry out the reaction.

[0036] 4) After the reaction in step 3) has proceeded for a period of time, the coarse particulate product in the reaction system is separated and aged. After aging, the product is then filtered, washed, and dried to obtain the copper-doped nickel-iron-manganese precursor material.

[0037] 5) The sodium-ion battery cathode material is obtained by mixing and calcining copper-doped nickel-iron-manganese precursor materials with sodium salt.

[0038] Steps 1) to 4) are the same as in the first implementation scheme.

[0039] Preferably, in step 5), the sodium salt is one or more of sodium carbonate, sodium bicarbonate, and sodium acetate. The molar ratio of the copper-doped nickel-iron-manganese precursor material to the sodium salt is 1:0.501 to 0.505.

[0040] Preferably, in step 5), ethanol is added as a mixing agent when mixing the copper-doped nickel-iron-manganese precursor material with the sodium salt.

[0041] Preferably, in step 5), the calcination temperature is 700–900°C, more preferably 750–850°C. The calcination duration is 3–48 h, more preferably 5–36 h.

[0042] In this invention, the molecular formula of the sodium battery cathode material can be represented as: Na(Ni) 1 / 3-x Cu x Fe 1 / 3 Mn 1 / 3 O2, where 0 ≤ x ≤ 0.3.

[0043] In this invention, gallic acid esters are used as antioxidants in the reaction process. Currently, the antioxidants used in the preparation of multi-component precursor materials are mostly inorganic salts such as sodium sulfite and sodium thiosulfate (e.g., patent CN116886646A), and organic substances such as ascorbic acid (e.g., patent CN118108269A). However, sulfite is alkaline in its solution, and ascorbic acid is acidic, both of which affect the precipitation process. The gallic acid esters proposed in this invention are organic lipids with strong free radical scavenging capabilities. During application, a small amount can demonstrate strong antioxidant capacity, and they can be effectively removed by subsequent ethanol washing, with almost no impurities introduced. Compared to sulfites, thiosulfates, and ascorbic acid, they are superior antioxidants.

[0044] In this invention, the production cycle of the precursor material mixing reaction can be shortened by adding seed crystals. Currently, the production cycle of some precursor material preparation processes is relatively long, such as patent CN117800404, where the longest production cycle reaches 210 hours. This invention can shorten the production cycle to less than 9 hours by first preparing crystals with a particle size range of less than 3 micrometers as seed crystals, and then preparing the precursor. This allows for the preparation of precursor particles with larger particle size and better morphology.

[0045] In this invention, a micro-complexing operation is performed on the mixed metal salt solution before the reaction, which improves the stability of the production process. Specifically, this invention first adds a small amount of complexing agent to the mixed metal salt solution to form a micro-complexed mixed metal salt solution, thereby increasing the concentration of complexed ions and reducing the concentration of free ions. When the micro-complexed mixed metal salt solution is added dropwise to the reaction vessel, the presence of complexed ions reduces the ability of ions to directly form corresponding hydroxides, slows down the release rate of metal ions, prevents the rapid formation of hydroxides and their rapid oxidation, improves the stability of the preparation process, and to some extent reduces the amount of ferrous hydroxide generated during the reaction. Simultaneously, when copper ion doping is present, it also improves the incompatibility of copper hydroxide during precipitation, significantly improving the uniformity of elemental distribution in the particles.

[0046] In this invention, by adding dispersants such as polyethylene glycol and polyvinyl alcohol, a series of problems such as impure phases, severe agglomeration, and uneven particle size distribution in samples prepared by traditional processes are solved. This reduces the possibility that small hydroxide crystals in the process may rapidly combine into large particles due to insufficient stirring, and significantly improves the particle size uniformity of the prepared material.

[0047] In this invention, the reaction is mainly divided into two stages. In the first stage, the growth of fine crystals on the seed crystals is promoted by adjusting the pH and ammonia concentration of the precipitation system. In the second stage, the product is classified by a hydrocyclone separator, with coarse particles entering the next process and fine particles returning to the reactor to continue the reaction, thus shortening the reaction time and optimizing the particle morphology of the product. Under the action of various improved conditions, the particle size, morphology, and bulk density of the product prepared by this invention are controlled, enabling the production of nickel-iron-manganese precursor materials that meet the requirements of different industries.

[0048] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0049] 1. The antioxidant used in the process of this invention is a gallic acid ester compound. Compared with antioxidants such as sulfites, thiosulfates, and ascorbic acid, this compound has less impact on the coprecipitation system. Moreover, due to its strong free radical binding ability, it can effectively play a protective role. It is also easy to remove by alcohol washing in the later stage and hardly introduces impurities.

[0050] 2. The process of this invention pre-adds a specific amount of complexing agent to the mixed metal salt solution to prepare a micro-complexed mixed metal salt solution. This reduces the concentration of free metal ions to a certain extent, slows down the release rate of metal ions, reduces the possibility of rapid formation of hydroxides and rapid oxidation, and improves the stability of the preparation process. When copper ions are used for doping, it can also solve the problem of copper hydroxide incompatibility.

[0051] 3: The process of this invention adopts a two-stage reaction approach. The first-stage reaction promotes the growth of fine crystals on the seed crystals by adjusting the pH, ammonia concentration and other conditions of the precipitation system. The second-stage reaction uses a hydrocyclone separator to classify the reaction products. Coarse particles enter the next process, while fine particles are returned to the reactor to continue the reaction. This greatly shortens the preparation cycle, and the prepared products have uniform particle size and regular morphology.

[0052] 4. The process of this invention also uses dispersants such as polyvinyl alcohol for particle size adjustment. The addition of dispersants limits the ability of small crystals to rapidly polymerize into large crystals to a certain extent, so that the prepared precursor material has good microstructure and uniform particle size distribution. Attached Figure Description

[0053] Figure 1 The image shows a SEM image of the copper-doped nickel-iron-manganese precursor material prepared in Example 1.

[0054] Figure 2 The image shows the XRD pattern of the copper-doped nickel-iron-manganese precursor material prepared in Example 1.

[0055] Figure 3 The diagram shows the composition ratio of the copper-doped nickel-iron-manganese precursor materials prepared in Examples 1 and 12, respectively.

[0056] Figure 4 The image shows the XRD pattern of the sodium battery cathode material prepared in Example 1.

[0057] Figure 5 This is a SEM image of the sodium battery cathode material prepared in Example 1.

[0058] Figure 6 The image shows the XRD pattern of the nickel-iron-manganese precursor material prepared in Example 15.

[0059] Figure 7This is a SEM image of the nickel-iron-manganese precursor material prepared in Example 15.

[0060] Figure 8 The image shows the EDS diagram of the nickel-iron-manganese precursor material prepared in Example 15.

[0061] Figure 9 The image shows the XRD pattern of the sodium battery cathode material prepared in Example 15.

[0062] Figure 10 This is a SEM image of the sodium battery cathode material prepared in Example 15.

[0063] Figure 11 This is a flowchart illustrating the overall process flow of the method described in this invention. Detailed Implementation

[0064] The technical solution of the present invention will be illustrated below with examples. The scope of protection sought by the present invention includes, but is not limited to, the following embodiments.

[0065] Example 1

[0066] (1) Add 150 mL of deoxygenated water to a 500 mL reactor, add methyl gallate as an antioxidant, add sodium hydroxide as a precipitant, and add polyvinyl alcohol (1788) as a dispersant; use a stirring paddle to stir at a uniform speed, and set the initial stirring speed to 300 rpm; wherein: control the concentration of methyl gallate in the reactor to be 0.04 mol / L, control the concentration of polyvinyl alcohol (1788) in the reactor to be 0.02 mol / L, and control the amount of sodium hydroxide added in the reactor to make the pH value of the system 11.5.

[0067] (2) Nitrogen gas is introduced as a protective gas and the nitrogen flow rate is set to 80 mL / min; the reaction vessel is heated until the reaction system temperature reaches and stabilizes at 55°C, and then ammonia water is added to the reaction vessel as a complexing agent, and the ammonia concentration in the reaction vessel is controlled to be 0.6 mol / L.

[0068] (3) Press Ni 2+ Cu 2+ Mn 2+ Fe 2+The molar ratio of nickel sulfate, copper sulfate, manganese sulfate, and ferrous sulfate was 0.24:0.09:0.33:0.33. A mixed metal salt solution was obtained by dissolving nickel sulfate, copper sulfate, manganese sulfate, and ferrous sulfate in deoxygenated water. Ammonia water (with a system concentration of 0.03 mol / L) was then added to the mixed metal salt solution to obtain a micro-complexed mixed metal salt solution. Under stirring conditions of 300 rpm and a temperature of 55°C, the micro-complexed mixed metal salt solution was added dropwise to the above-mentioned reaction vessel at a rate of 12.5 mL / min (the amount of micro-complexed mixed metal salt solution was such that the system concentration of the mixed metal salt in the reaction vessel was 0.45 mol / L). After all the materials were added to the reaction vessel, the reaction was continued for 6 hours to carry out the first stage of the reaction.

[0069] (4) After the first reaction stage is completed, the stirring speed and temperature of the system are kept constant for the second reaction stage. During this process, every hour, a portion (100 mL at a time, for 10 hours) of the solution is pumped into a hydrocyclone separator for separation. The coarse particles (particle size greater than 10 micrometers) obtained from the separation are sent to the aging tank, while the remaining fine particles are returned to the reactor. After the second reaction stage is completed, the material in the aging tank is further aged for 6 hours, then filtered, and the solid product is washed sequentially with deoxygenated water and anhydrous ethanol. Finally, after drying, copper-doped nickel-iron-manganese precursor material is obtained.

[0070] (5) The copper-doped nickel-iron-manganese precursor material prepared above was ground and mixed with sodium carbonate in a mortar at a molar ratio of 1:0.501. During the process, alcohol was added to ensure uniform mixing. The mixed material was then placed in an oven and dried at 100°C. The dried sample was then placed in an alumina crucible and calcined in an electric furnace. The initial calcination temperature was set at 550°C, and after calcination for 5 hours, the temperature was slowly increased (15°C / min) to 850°C and calcined for another 20 hours. After calcination was completed and the furnace was allowed to return to room temperature, the sample was removed. The sample was then ground and sieved to obtain the sodium battery cathode material.

[0071] Example 2

[0072] (1) Add 150 mL of deoxygenated water to a 500 mL reactor, add methyl gallate as an antioxidant, add sodium hydroxide as a precipitant, and add polyvinyl alcohol (1788) as a dispersant; use a stirring paddle to stir at a constant speed, setting the initial stirring speed to 300 rpm; wherein: control the concentration of methyl gallate in the reactor to be 0.04 mol / L, control the concentration of polyvinyl alcohol (1788) in the reactor to be 0.02 mol / L, and control the amount of sodium hydroxide added in the reactor to make the pH value of the system 10.5.

[0073] (2) Nitrogen gas is introduced as a protective gas and the nitrogen flow rate is set to 80 mL / min; the reaction vessel is heated until the reaction system temperature reaches and stabilizes at 55°C, and then ammonia water is added to the reaction vessel as a complexing agent, and the ammonia concentration in the reaction vessel is controlled to be 0.6 mol / L.

[0074] (3) Press Ni 2+ Cu 2+ Mn 2+ Fe 2+ The molar ratio of nickel sulfate, copper sulfate, manganese sulfate, and ferrous sulfate was 0.24:0.09:0.33:0.33. A mixed metal salt solution was obtained by dissolving nickel sulfate, copper sulfate, manganese sulfate, and ferrous sulfate in deoxygenated water. Ammonia water (with a system concentration of 0.03 mol / L) was then added to the mixed metal salt solution to obtain a micro-complexed mixed metal salt solution. Under stirring conditions of 300 rpm and a temperature of 55°C, the micro-complexed mixed metal salt solution was added dropwise to the above-mentioned reaction vessel at a rate of 12.5 mL / min (the amount of micro-complexed mixed metal salt solution was such that the system concentration of the mixed metal salt in the reaction vessel was 0.45 mol / L). After all the materials were added to the reaction vessel, the reaction was continued for 6 hours to carry out the first stage of the reaction.

[0075] (4) After the first reaction stage is completed, the stirring speed and temperature of the system are kept constant for the second reaction stage. During this process, every hour, a portion (100 mL at a time, for 10 hours) of the solution is pumped into a hydrocyclone separator for separation. The coarse particles (particle size greater than 10 micrometers) obtained from the separation are sent to the aging tank, while the remaining fine particles are returned to the reactor. After the second reaction stage is completed, the material in the aging tank is further aged for 6 hours, then filtered, and the solid product is washed sequentially with deoxygenated water and anhydrous ethanol. Finally, after drying, copper-doped nickel-iron-manganese precursor material is obtained.

[0076] (5) The copper-doped nickel-iron-manganese precursor material prepared above was ground and mixed with sodium carbonate in a mortar at a molar ratio of 1:0.501. During the process, alcohol was added to ensure uniform mixing. The mixed material was then placed in an oven and dried at 100°C. The dried sample was then placed in an alumina crucible and calcined in an electric furnace. The initial calcination temperature was set at 550°C, and after calcination for 5 hours, the temperature was slowly increased (15°C / min) to 850°C and calcined for another 20 hours. After calcination was completed and the furnace was allowed to return to room temperature, the sample was removed. The sample was then ground and sieved to obtain the sodium battery cathode material.

[0077] Example 3

[0078] Example 2 was repeated, except that methyl gallate, which is an antioxidant, was replaced with ethyl gallate.

[0079] Example 4

[0080] Example 2 was repeated, except that methyl gallate, which is an antioxidant, was replaced with isopropyl gallate.

[0081] Example 5

[0082] Example 2 was repeated, except that methyl gallate, which is an antioxidant, was replaced with gallic acid.

[0083] Example 6

[0084] Example 2 was repeated, except that polyvinyl alcohol (1788) used as a dispersant was replaced with polyvinyl alcohol (2488).

[0085] Example 7

[0086] Example 2 was repeated, except that the polyvinyl alcohol (1788) used as a dispersant was replaced with polyethylene glycol (1500).

[0087] Example 8

[0088] Example 2 was repeated, except that polyvinyl alcohol (1788) used as a dispersant was replaced with polyethylene glycol (4000).

[0089] Example 9

[0090] Repeat Example 2, except that the ammonia water used as the complexing agent is replaced with citric acid.

[0091] Example 10

[0092] Repeat Example 2, except that the ammonia water used as the complexing agent is replaced with oxalic acid.

[0093] Example 11

[0094] Repeat Example 2, except that the ammonia water used as the complexing agent is replaced with tartaric acid.

[0095] Example 12

[0096] Example 2 was repeated, except that the amount of ammonia added was controlled so that the concentration of ammonia in the micro-complexed mixed metal salt solution was 0.01 mol / L.

[0097] Example 13

[0098] Repeat Example 2, except that the amount of ammonia added is controlled so that the concentration of ammonia in the micro-complexed mixed metal salt solution is 0.05 mol / L.

[0099] Example 14

[0100] Repeat Example 2, except that the reaction time for the first stage is controlled to be 9 hours.

[0101] Example 15

[0102] (1) Add 150 mL of deoxygenated water to a 500 mL reactor, add methyl gallate as an antioxidant, add sodium hydroxide as a precipitant, and add polyvinyl alcohol (1788) as a dispersant; use a stirring paddle to stir at a uniform speed, and set the initial stirring speed to 400 rpm; wherein: control the concentration of methyl gallate in the reactor to be 0.045 mol / L, control the concentration of polyvinyl alcohol (1788) in the reactor to be 0.02 mol / L, and control the amount of sodium hydroxide added in the reactor to make the pH value of the system 11.

[0103] (2) Nitrogen gas is introduced as a protective gas and the nitrogen flow rate is set to 80 mL / min; the reaction vessel is heated until the reaction system temperature reaches and stabilizes at 65°C, and then ammonia water is added to the reaction vessel as a complexing agent, and the ammonia concentration in the reaction vessel is controlled to be 0.6 mol / L.

[0104] (3) Press Ni 2+ Mn 2+ Fe 2+ Nickel sulfate, manganese sulfate, and ferrous sulfate were dissolved in deoxygenated water at a molar ratio of 1:1:1 to obtain a mixed metal salt solution. Ammonia water (with a system concentration of 0.04 mol / L) was then added to the mixed metal salt solution to obtain a micro-complexed mixed metal salt solution. Under stirring conditions of 400 rpm and a temperature of 65°C, the micro-complexed mixed metal salt solution was added dropwise to the above-mentioned reaction vessel at a rate of 12.5 mL / min (the amount of micro-complexed mixed metal salt solution was such that the system concentration of the mixed metal salt in the reaction vessel was 0.45 mol / L). After all the materials were added to the reaction vessel, the current reaction conditions were maintained for 6 hours to carry out the first stage of the reaction.

[0105] (4) After the first reaction stage is completed, the stirring speed and temperature of the system are kept constant for the second reaction stage. During this process, every hour, a portion (100 mL at a time, for 10 hours) of the solution is pumped into a hydrocyclone separator for separation. The coarse particles (particle size greater than 10 micrometers) obtained from the separation are sent to the aging tank, while the remaining fine particles are returned to the reactor. After the second reaction stage is completed, the material in the aging tank is aged for another 6 hours, then filtered, and the solid product is washed sequentially with deoxygenated water and anhydrous ethanol. Finally, after drying, the 111-type copper-doped nickel-iron-manganese precursor material is obtained.

[0106] (5) The copper-doped nickel-iron-manganese precursor material prepared above was ground and mixed with sodium carbonate in a mortar at a molar ratio of 1:0.505. During the process, alcohol was added to ensure uniform mixing. The mixed material was then placed in an oven and dried at 100°C. The dried sample was then placed in an alumina crucible and calcined in an electric furnace. The initial calcination temperature was set at 500°C, and after calcination for 4 hours, the temperature was slowly increased (15°C / min) to 750°C and calcined for another 20 hours. After calcination was completed and the furnace was allowed to return to room temperature, the sample was removed. The obtained sample was then ground and sieved to obtain the sodium battery cathode material.

[0107] Comparative Example 1

[0108] Example 2 was repeated, except that methyl gallate, which is used as an antioxidant, was replaced with sodium sulfite.

[0109] Comparative Example 2

[0110] Example 2 was repeated, except that methyl gallate, which is used as an antioxidant, was replaced with sodium persulfate.

[0111] Comparative Example 3

[0112] Repeat Example 2, except that the amount of ammonia added is controlled so that the concentration of ammonia in the micro-complexed mixed metal salt solution is 0 mol / L.

[0113] Comparative Example 4

[0114] Example 2 was repeated, except that the amount of ammonia added was controlled so that the concentration of ammonia in the micro-complexed mixed metal salt solution was 0.08 mol / L.

[0115] Comparative Example 5

[0116] Repeat Example 15, except that the amount of ammonia added is controlled so that the concentration of ammonia in the micro-complexed mixed metal salt solution is 0 mol / L.

[0117] Comparative Example 6

[0118] Example 15 was repeated, except that the amount of ammonia added was controlled so that the concentration of ammonia in the micro-complexed mixed metal salt solution was 0.08 mol / L.

[0119] Comparison table of performance of products from various embodiments and comparative examples:

[0120]

[0121]

[0122] As can be seen from the table above, the sodium battery cathode materials prepared using the copper-doped nickel-iron-manganese precursor materials and the undoped nickel-iron-manganese precursor materials prepared according to the various embodiments of the present invention all have good discharge specific capacity and excellent cycle efficiency (i.e., 1C discharge specific capacity retention rate), and are significantly better than the sodium battery cathode materials prepared by Comparative Example 1 and Comparative Example 2.

Claims

1. A method for preparing copper-doped nickel-iron-manganese precursor materials, characterized in that: The method includes: 1) First, add deoxygenated water, antioxidant, precipitant, and dispersant to the reaction vessel and start stirring. Then, introduce a protective gas and heat. Finally, add a complexing agent and mix thoroughly to obtain the reaction base liquid. The antioxidant is one or more of methyl gallate, ethyl gallate, propyl gallate, isopropyl gallate, butyl gallate, tert-butyl gallate, and gallic acid. The amount of antioxidant added is such that the system concentration is 0.02~0.05 mol / L. The complexing agent is one or more of ammonia, citric acid, oxalic acid, and tartaric acid. The amount of complexing agent added is such that the system concentration is 0.3~1 mol / L. 2) A mixed metal salt solution is obtained by mixing copper salt solution, nickel salt solution, ferrous salt solution, and manganese salt solution. Then, a complexing agent is added to the mixed metal salt solution to obtain a micro-complexed mixed metal salt solution. In the micro-complexed mixed metal salt solution, the concentration of the complexing agent is 0.02~0.05 mol / L. 3) Add the micro-complexed mixed metal salt solution obtained in step 2) to the reaction substrate of step 1) to carry out the reaction; the amount of micro-complexed mixed metal salt solution added is such that the concentration of the mixed metal salt in the reaction system is 0.2~0.5 mol / L; 4) After the reaction in step 3) has been going on for a period of time, the coarse particulate product in the reaction system is separated and aged. After aging, the product is filtered, washed and dried in sequence to obtain the copper-doped nickel-iron-manganese precursor material.

2. The method according to claim 1, characterized in that: The amount of antioxidant added is such that the system concentration is 0.02~0.045 mol / L.

3. The method according to claim 1, characterized in that: In step 1), the precipitant is an alkali.

4. The method according to claim 3, characterized in that: In step 1), the precipitant is sodium hydroxide.

5. The method according to claim 3, characterized in that: In step 1), the amount of precipitant added is such that the pH of the system is 9-13.

6. The method according to claim 5, characterized in that: In step 1), the amount of precipitant added is such that the pH of the system is 10-12.

7. The method according to any one of claims 1-6, characterized in that: In step 1), the dispersant is polyethylene glycol and / or polyvinyl alcohol.

8. The method according to claim 7, characterized in that: In step 1), the dispersant is polyethylene glycol and / or polyvinyl alcohol with an average molecular weight of 800 to 8000.

9. The method according to claim 8, characterized in that: In step 1), the dispersant is one or more of polyethylene glycol 1000, polyethylene glycol 1500, polyethylene glycol 2000, polyethylene glycol 4000, polyethylene glycol 6000, polyvinyl alcohol 1788, and polyvinyl alcohol 2488.

10. The method according to claim 7, characterized in that: In step 1), the amount of dispersant added is such that the system concentration is 0.02~0.05 mol / L.

11. The method according to claim 10, characterized in that: In step 1), the amount of dispersant added is such that the system concentration is 0.02~0.04 mol / L.

12. The method according to any one of claims 1-6 and 8-11, characterized in that: The amount of complexing agent added is such that the concentration of the system is 0.3~0.8 mol / L.

13. The method according to any one of claims 1-6 and 8-11, characterized in that: In step 1), the protective gas is an inert gas and / or nitrogen; the flow rate of the protective gas is not less than 80 mL / min; and / or In step 1), the stirring speed shall not be less than 100 rpm; In step 1), the heating is to heat the system to 40~70°C.

14. The method according to claim 13, characterized in that: In step 1), the flow rate of the protective gas is 90~150 mL / min; and / or In step 1), the stirring speed is 200~600 rpm; In step 1), the heating is to heat the system to 45~65°C.

15. The method according to any one of claims 1-6, 8-11, and 14, characterized in that: In step 2), the copper salt is one or more of copper sulfate, copper nitrate, and copper chloride; the nickel salt is one or more of nickel sulfate, nickel nitrate, and nickel chloride; the ferrous salt is one or more of ferrous sulfate, ferrous nitrate, and ferrous chloride; and the manganese salt is one or more of manganese sulfate, manganese nitrate, and manganese chloride.

16. The method according to claim 15, characterized in that: In a mixed metal salt solution, the molar ratio of nickel ions, copper ions, manganese ions, and ferrous ions is (1-x):x:0.8~1.2:0.8~1.2, where 0<x≤0.

3.

17. The method according to claim 15, characterized in that: In the micro-complexed mixed metal salt solution, the concentration of the complexing agent is 0.02~0.04 mol / L.

18. The method according to any one of claims 1-6, 8-11, 14, and 16-17, characterized in that: In step 3), the amount of the micro-complexed mixed metal salt solution added is such that the concentration of the mixed metal salt in the reaction system is 0.25~0.45 mol / L; and / or In step 3), the reaction time is not less than 1 hour; and / or In step 4), the separation is a cyclone separation; the particle size of the coarse particulate product is not less than 10 micrometers.

19. A method for preparing a sodium battery cathode material, characterized in that: The method includes: 1) First, add deoxygenated water, antioxidant, precipitant, and dispersant to the reaction vessel and start stirring. Then, introduce a protective gas and heat. Finally, add a complexing agent and mix thoroughly to obtain the reaction base liquid. The antioxidant is one or more of methyl gallate, ethyl gallate, propyl gallate, isopropyl gallate, butyl gallate, tert-butyl gallate, and gallic acid. The amount of antioxidant added is such that the system concentration is 0.02~0.05 mol / L. The complexing agent is one or more of ammonia, citric acid, oxalic acid, and tartaric acid. The amount of complexing agent added is such that the system concentration is 0.3~1 mol / L. 2) A mixed metal salt solution is obtained by mixing copper salt solution, nickel salt solution, ferrous salt solution, and manganese salt solution. Then, a complexing agent is added to the mixed metal salt solution to obtain a micro-complexed mixed metal salt solution. In the micro-complexed mixed metal salt solution, the concentration of the complexing agent is 0.02~0.05 mol / L. 3) Add the micro-complexed mixed metal salt solution obtained in step 2) to the reaction substrate of step 1) to carry out the reaction; the amount of micro-complexed mixed metal salt solution added is such that the concentration of the mixed metal salt in the reaction system is 0.2~0.5 mol / L; 4) After the reaction in step 3) has been going on for a period of time, the coarse particulate product in the reaction system is separated and aged. After aging, the product is filtered, washed and dried in sequence to obtain the copper-doped nickel-iron-manganese precursor material. 5) The sodium-ion battery cathode material is obtained by mixing and calcining copper-doped nickel-iron-manganese precursor material with sodium salt.

20. The method according to claim 19, characterized in that: The amount of antioxidant added is such that the system concentration is 0.02~0.045 mol / L.

21. The method according to claim 19, characterized in that: In step 1), the precipitant is an alkali.

22. The method according to claim 21, characterized in that: In step 1), the precipitant is sodium hydroxide.

23. The method according to claim 21, characterized in that: In step 1), the amount of precipitant added is such that the pH of the system is 9-13.

24. The method according to claim 23, characterized in that: In step 1), the amount of precipitant added is such that the pH of the system is 10-12.

25. The method according to any one of claims 19-24, characterized in that: In step 1), the dispersant is polyethylene glycol and / or polyvinyl alcohol.

26. The method according to claim 25, characterized in that: In step 1), the dispersant is polyethylene glycol and / or polyvinyl alcohol with an average molecular weight of 800 to 8000.

27. The method according to claim 26, characterized in that: In step 1), the dispersant is one or more of polyethylene glycol 1000, polyethylene glycol 1500, polyethylene glycol 2000, polyethylene glycol 4000, polyethylene glycol 6000, polyvinyl alcohol 1788, and polyvinyl alcohol 2488.

28. The method according to claim 25, characterized in that: In step 1), the amount of dispersant added is such that the system concentration is 0.02~0.05 mol / L.

29. The method according to claim 28, characterized in that: In step 1), the amount of dispersant added is such that the system concentration is 0.02~0.04 mol / L.

30. The method according to any one of claims 19-24 and 26-29, characterized in that: The amount of complexing agent added is such that the concentration of the system is 0.3~0.8 mol / L.

31. The method according to any one of claims 19-24 and 26-29, characterized in that: In step 1), the protective gas is an inert gas and / or nitrogen; the flow rate of the protective gas is not less than 80 mL / min; and / or In step 1), the stirring speed shall not be less than 100 rpm; In step 1), the heating is to heat the system to 40~70°C.

32. The method according to claim 31, characterized in that: In step 1), the flow rate of the protective gas is 90~150 mL / min; and / or In step 1), the stirring speed is 200~600 rpm; In step 1), the heating is to heat the system to 45~65°C.

33. The method according to any one of claims 19-24, 26-29, and 32, characterized in that: In step 2), the copper salt is one or more of copper sulfate, copper nitrate, and copper chloride; the nickel salt is one or more of nickel sulfate, nickel nitrate, and nickel chloride; the ferrous salt is one or more of ferrous sulfate, ferrous nitrate, and ferrous chloride; and the manganese salt is one or more of manganese sulfate, manganese nitrate, and manganese chloride.

34. The method according to claim 33, characterized in that: In a mixed metal salt solution, the molar ratio of nickel ions, copper ions, manganese ions, and ferrous ions is (1-x):x:0.8~1.2:0.8~1.2, where 0<x≤0.

3.

35. The method according to claim 33, characterized in that: In the micro-complexed mixed metal salt solution, the concentration of the complexing agent is 0.02~0.04 mol / L.

36. The method according to any one of claims 19-24, 26-29, 32, and 34-35, characterized in that: In step 3), the amount of the micro-complexed mixed metal salt solution added is such that the concentration of the mixed metal salt in the reaction system is 0.25~0.45 mol / L; and / or In step 3), the reaction time is not less than 1 hour; and / or In step 4), the separation is a cyclone separation; the particle size of the coarse particulate product is not less than 10 micrometers.

37. The method according to any one of claims 19-24, 26-29, 32, and 34-35, characterized in that: In step 5), the sodium salt is one or more of sodium carbonate, sodium bicarbonate, and sodium acetate; the molar ratio of the copper-doped nickel-iron-manganese precursor material to the sodium salt is 1:0.50~0.

52.

38. The method according to claim 37, characterized in that: In step 5), ethanol is added as a mixing agent when mixing the copper-doped nickel-iron-manganese precursor material with sodium salt.

39. The method according to claim 37, characterized in that: In step 5), the calcination temperature is 700~900℃; the calcination time is 3~48h.

40. The method according to claim 39, characterized in that: In step 5), the calcination temperature is 750~850℃; the calcination time is 5~36h.

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