Preparation method of ferric sodium pyrophosphate positive electrode material for sodium ions
By optimizing the preparation process and controlling the reaction conditions, the problems of low conductivity and impurity generation of sodium iron pyrophosphate positive electrode materials were solved, the preparation of high-purity materials was achieved, its electrochemical performance and cycle stability were improved, and the scope of application was expanded.
Patent Information
- Application Number
- CN202510991408.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-18
- Publication Date
- 2025-10-21
AI Technical Summary
The existing sodium iron phosphate pyrophosphate positive electrode material has low conductivity and is prone to produce NaFeP2O7 impurity phase during the preparation process, which affects the material performance.
An improved preparation method is adopted, including optimizing the raw material ratio and a two-step sintering method. Through ball milling, drying, sintering and screening steps, the reaction conditions are controlled, the generation of impurities is reduced, and the purity and electrical conductivity of the material are improved.
The electrochemical performance of sodium iron pyrophosphate positive electrode material is improved, its cycle stability and safety are enhanced, and its application range is broadened to meet different energy storage needs.
Smart Images
Figure CN120817588A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of new energy storage technology, and in particular to a method for preparing a sodium iron phosphate pyrophosphate positive electrode material for sodium ions. Background Art
[0002] Currently, research in the field of sodium-ion batteries focuses on three mainstream cathode materials: layered materials, Prussian blue and its derivatives, and phosphate-based materials. While layered materials offer high energy density, their cycling and structural stability may decline during long-term charge and discharge, limiting their application. Prussian blue and its derivatives have attracted attention for their excellent electrochemical properties, but their stability under high-voltage operation remains a challenge. Furthermore, the synthesis of these materials may involve environmentally unfriendly chemicals, potentially impacting the environment. As a novel cathode material, sodium ferrous pyrophosphate (NFPP) exhibits excellent performance under long-term cycling and high-rate charge and discharge conditions, particularly its excellent cycling stability and high theoretical specific capacity, due to its unique crystal structure and chemical stability.
[0003] At present, the preparation methods of sodium ferric pyrophosphate mainly include solid-phase method, freeze-drying method, sol-gel method, spray drying method, etc. However, the materials synthesized by these methods generally have problems such as low material conductivity. In addition, since the material has a similar crystal structure to NaFeP2O7, NaFeP2O7 impurities are easily produced during the preparation process, thereby affecting the performance of the NFPP material. Summary of the Invention
[0004] Therefore, in order to solve the above problems and shortcomings, the present invention provides a method for preparing a sodium ion-containing sodium iron phosphate pyrophosphate positive electrode material, a method for preparing a sodium ion-containing sodium iron phosphate pyrophosphate positive electrode material, comprising the following steps: S1. Ingredients: One or more of sodium pyrophosphate, sodium carbonate, sodium dihydrogen phosphate, and sodium phosphate are selected as sodium sources; one or more of ferrous oxalate, ferric phosphate, ferric oxide, and iron powder are selected as iron sources; one or more of ammonium dihydrogen phosphate, phosphoric acid, sodium dihydrogen phosphate, and ferric phosphate are selected as phosphorus sources; one or more of glucose, citric acid, and sucrose are selected as carbon sources; and the ingredients are prepared according to the ratio of the four elements Na, Fe, P, and C being 4:2.92:4:0.97.
[0005] S2. Dissolution: Weigh some of the ingredients in S1 as reaction raw materials, dissolve the raw materials in 100 L of anhydrous ethanol, and obtain suspension A by stirring.
[0006] S3. Ball milling: Transfer the suspension A obtained in S2 to a ball mill, set the ball-to-material ratio to 1:8, and obtain suspension B after ball milling.
[0007] S4. Drying: Transfer the suspension B obtained in S3 to an oven and dry it to obtain a precursor.
[0008] S5. Sintering: The precursor obtained in step S4 is sintered in a nitrogen atmosphere furnace using a two-step sintering method to obtain a carbon-coated product.
[0009] S6. Cooling and screening: After the temperature drops to room temperature, use a 325-mesh sieve to screen the initial product in S5 to obtain the final product.
[0010] Preferably, in S1, the sodium source is preferably sodium pyrophosphate, the iron source is preferably ferrous oxalate, the phosphorus source is preferably ammonium dihydrogen phosphate, and the carbon source is preferably citric acid, and the purity of the raw materials is all 98%.
[0011] Preferably, the amount of ingredients used in S2 is 31.25 g, and the solid content of the obtained suspension A is 23.8%.
[0012] Preferably, the baking temperature of the oven in S4 is set to 90°C, the drying time is set to 10-12 hours, and the solvent is evaporated until no solvent remains. Preferably, in the two-step sintering method S5, the sintering temperature of the first step is controlled at 300° C.-450° C., and the sintering time is set to 3 hours.
[0013] Preferably, in the two-step sintering method S5, the sintering temperature of the second step is controlled at 500-580° C., and the sintering time is set to 8 hours.
[0014] Preferably, in the S5 two-step sintering method, the heating rate of the sintering process is 5° C. / min, and the sintering is performed in a nitrogen atmosphere furnace.
[0015] Preferably, in the two-step sintering method S5, the sintering temperature of the second step is controlled at 500-580° C., and the sintering time is set to 8 hours.
[0016] The beneficial effects of the present invention can be reflected in the following aspects after specific analysis: Advantage 1: By improving the preparation process and optimizing the material structure, the electrochemical properties of sodium ferric pyrophosphate can be improved, and its charge and discharge efficiency, cycle stability and safety can be improved, so that it can perform well in various application scenarios, further optimize its structure and performance, and broaden its application range to meet the energy storage needs of different fields.
[0017] Advantage 2: Optimizing the raw material ratio, adopting a non-stoichiometric ratio in the ratio calculation process, improving the electrical conductivity and electron migration rate of the material, the reaction temperature of the present invention is relatively mild, the preparation process is efficient and the energy consumption is low, and the prepared positive electrode material has a high discharge capacity and good cycle performance. Moreover, by controlling the reaction means, the generation of impurities in the material synthesis process is reduced. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Figure 1 The present invention is a flow chart of a method for preparing a sodium iron phosphate pyrophosphate positive electrode material for sodium ions. DETAILED DESCRIPTION
[0019] The present invention will be described in detail below with reference to the accompanying drawings, clearly and completely describing the technical solutions in the embodiments of the present invention. The same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention. It should be understood that ordinal numbers and directional descriptions, such as "first," "second," "third," "upper, lower, left, right," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, in the description of the present invention, unless otherwise expressly provided or limited, the terms "connected" and "connected" should be understood broadly and should not be construed as limiting the present invention.
[0020] The following is a further detailed description of the technical solution of the present invention in conjunction with the accompanying drawings and specific implementation methods. Figure 1 As shown, the present application provides a method for preparing a sodium ion sodium iron pyrophosphate positive electrode material, comprising the following steps: Step 1, ingredients: select one or more of sodium pyrophosphate, sodium carbonate, sodium dihydrogen phosphate, and sodium phosphate as the sodium source; select one or more of ferrous oxalate, ferric phosphate, ferric oxide, and iron powder as the iron source; select one or more of ammonium dihydrogen phosphate, phosphoric acid, sodium dihydrogen phosphate, and ferric phosphate as the phosphorus source; select one or more of glucose, citric acid, and sucrose as the carbon source; and prepare the ingredients according to the ratio of the four elements Na, Fe, P, and C of 4:2.92:4:0.97.
[0021] Step 2, dissolution: Weigh some of the ingredients in step 1 as reaction raw materials, dissolve the raw materials in 100 L of anhydrous ethanol (containing a low-boiling point solvent) in an agate jar, and stir briefly with a glass rod to obtain suspension A.
[0022] Step 3, ball milling and drying: transfer the suspension A obtained in step 2 to a ball mill, weigh the relevant raw materials and add them to an agate jar containing a low-boiling point solvent, and use a glass rod to simply stir and mix, setting the grinding ball-to-material ratio to 1:8. 5mm zirconium balls can be added to the ball-to-material ratio, and the mass of the zirconium balls is 9 times the total amount of the raw materials. The raw materials are mixed by ball milling at a speed of 450rpm for 5h in a set planetary ball mill to make the raw material monomers evenly dispersed in the solvent. After ball milling, suspension B is obtained, and then suspension B is transferred to an oven and dried to obtain a precursor.
[0023] Step 4, sintering: The precursor obtained in step 4 is sintered in a nitrogen atmosphere furnace using a two-step sintering method to obtain a carbon-coated product.
[0024] Step 5, cooling and screening: After the temperature drops to room temperature, use a 325-mesh sieve to screen the initial product in step 5 to obtain the final product.
[0025] As an embodiment, it should be noted that: sodium pyrophosphate is preferably selected as the sodium source, ferrous oxalate is preferably selected as the iron source, ammonium dihydrogen phosphate is preferably selected as the phosphorus source, and citric acid is preferably selected as the carbon source. The purity of the above raw materials is relatively high, and can reach 98%.
[0026] In the actual preparation stage, 31.25 g of mixed raw materials were selected, and the solid content of suspension A and suspension B obtained was about 23.8%. The obtained precursor was about 30 g, and the actual final positive electrode material was about 18 g.
[0027] In the drying stage, the baking temperature of the oven is set to 90° C., and the drying time is set to 10-12 h. When the suspension B evaporates until no solvent remains, the pellets are separated with a sieve to obtain the precursor of the sodium iron pyrophosphate positive electrode material.
[0028] A two-step sintering method is used. In the first step, the sintering temperature is controlled at 300℃-450℃, and the sintering time is set to 3h; in the second step, the sintering temperature is controlled at 500-580℃, and the sintering time is set to 8h. In the above two-step sintering method, the heating rate of the sintering process is 5℃ / min, and both are sintered in a nitrogen atmosphere furnace. Nitrogen, as an inert gas, can effectively isolate oxygen, avoid oxidation at high temperature, and make the precursor structure denser.
[0029] In summary, the method for preparing sodium ferric phosphate pyrophosphate positive electrode material for sodium ions of the present invention reduces the generation of impurities during synthesis by optimizing the raw material ratio, introducing crystal defects, controlling reaction conditions, etc., thereby achieving the preparation of high-purity sodium ferric phosphate pyrophosphate.
[0030] The above are merely embodiments of the present invention, and common knowledge such as the known specific structures and characteristics of the scheme are not described in detail here. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the structure of the present invention, and these should also be regarded as the scope of protection of the present invention. These will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the description can be used to interpret the content of the claims.
Claims
1. A method for preparing a sodium ion sodium iron pyrophosphate positive electrode material, characterized in that: The steps include: S1. Ingredients: One or more of sodium pyrophosphate, sodium carbonate, sodium dihydrogen phosphate, and sodium phosphate are selected as sodium sources; one or more of ferrous oxalate, ferric phosphate, ferric oxide, and iron powder are selected as iron sources; one or more of ammonium dihydrogen phosphate, phosphoric acid, sodium dihydrogen phosphate, and ferric phosphate are selected as phosphorus sources; one or more of glucose, citric acid, and sucrose are selected as carbon sources; and the ingredients are prepared according to the ratio of Na, Fe, P, and C being 4:2.92:4:0.97; S2. Dissolution: Weigh some of the ingredients in S1 as reaction raw materials, dissolve the raw materials in 100 L of anhydrous ethanol, and obtain suspension A by stirring; S3, ball milling: transfer the suspension A obtained in S2 into a ball mill, set the ball-to-material ratio to 1:8, and obtain suspension B after ball milling; S4, drying: transferring the suspension B obtained in S3 to an oven and drying the suspension to obtain a precursor; S5, sintering: sintering the precursor obtained in step S4 in a nitrogen atmosphere furnace using a two-step sintering method to obtain a carbon-coated product; S6. Cooling and screening: After the temperature drops to room temperature, use a 325-mesh sieve to screen the initial product in S5 to obtain the final product.
2. The method for preparing a sodium ion sodium iron pyrophosphate positive electrode material according to claim 1, characterized in that: The sodium source described in S1 is preferably sodium pyrophosphate, the iron source is preferably ferrous oxalate, the phosphorus source is preferably ammonium dihydrogen phosphate, and the carbon source is preferably citric acid, and the purity of the raw materials is 98%.
3. The method for preparing a sodium ion sodium iron pyrophosphate positive electrode material according to claim 1, characterized in that: The amount of ingredients used in S2 is 31.25 g, and the solid content of the obtained suspension A is 23.8%.
4. The method for preparing a sodium ion sodium iron pyrophosphate positive electrode material according to claim 1, characterized in that: The baking temperature of the oven in S4 is set to 90° C., and the drying time is set to 10-12 hours, and the solvent is evaporated until no solvent remains.
5. The method for preparing a sodium ion sodium iron pyrophosphate positive electrode material according to claim 1, characterized in that: In the S5 two-step sintering method, the sintering temperature of the first step is controlled at 300° C.-450° C., and the sintering time is set to 3 hours.
6. The method for preparing a sodium ferric pyrophosphate positive electrode material for sodium ions according to claim 1, characterized in that: In the S5 two-step sintering method, the sintering temperature of the second step is controlled at 500-580° C., and the sintering time is set to 8 hours.
7. The method for preparing a sodium ion sodium iron pyrophosphate positive electrode material according to claim 1, characterized in that: In the S5 two-step sintering method, the heating rate of the sintering process is 5° C. / min, and the sintering is performed in a nitrogen atmosphere furnace.
8. The method for preparing a sodium ion sodium iron pyrophosphate positive electrode material according to claim 1, characterized in that: In the S5 two-step sintering method, the sintering temperature of the second step is controlled at 500-580° C., and the sintering time is set to 8 hours.