CN-118062820-B - Method for synthesizing ferric sodium pyrophosphate cathode material by utilizing ferric phosphate

Abstract

The invention relates to the technical field of sodium ion battery anode materials, and discloses a method for synthesizing a sodium ferric pyrophosphate anode material by utilizing ferric phosphate, which comprises the following steps of 1, adding ferric phosphate, a chelating agent, a sodium source, a phosphorus source and a carbon source into water to prepare a mixed solution; and 2, heating and stirring the mixed solution until the solution is clear, and performing spray drying on the clear solution to obtain precursor powder, and sintering the precursor powder in an inert atmosphere to obtain the sodium ferric phosphate anode material Na 4 Fe 3 (PO 4 ) 2 (P 2 O 7 ) @ C. According to the invention, through an ionization balance mechanism, the ferric phosphate and the chelating agent exist in an ionic form in the water phase, so that the synthesis time is effectively shortened, the problem that an associated inert phase is easy to generate in the material synthesis process is solved, and the uniformity of the sodium ferric phosphate generated by the reaction is improved.

Inventors

• YANG YEFENG
• XIA QIBO
• Ren Gaoya
• LI JIAMING

Assignees

• 浙江理工大学

Dates

Publication Date

20260505

Application Date

20240226

Claims (7)

1. 1. A method for synthesizing a sodium ferric pyrophosphate cathode material by utilizing ferric phosphate, which is characterized by comprising the following steps: The method comprises the steps of 1, adding ferric phosphate, a chelating agent, a sodium source, a phosphorus source and a carbon source into water to prepare a mixed solution, wherein the chelating agent is ethylenediamine tetraacetic acid, the molar ratio of the ferric phosphate to the chelating agent is (1-5) 1, the molar ratio of the ferric phosphate to the carbon source is (4-7) 1, and the sodium source and the phosphorus source are supplemented according to the molar ratio Na: fe: P=4:3:4 in the mixed solution; step 2, heating and stirring the mixed solution at the temperature of 60-80 ℃ for 0.5-1 h until the solution is clear; Step 3, spray drying the clarified solution to obtain precursor powder; and 4, sintering the precursor powder in an inert atmosphere to obtain the sodium ferric pyrophosphate phosphate anode material Na 4 Fe 3 (PO 4 ) 2 (P 2 O 7 ) @ C.
2. 2. The method for synthesizing ferric sodium pyrophosphate according to claim 1 wherein said carbon source in step 1 is at least one of polyvinylpyrrolidone, dopamine hydrochloride, tartaric acid, glucose, sucrose, starch, maltose and dextrin.
3. 3. The method for synthesizing ferric sodium pyrophosphate positive electrode material using ferric phosphate according to claim 1, wherein said sodium source in step 1 is at least one of sodium carbonate, sodium bicarbonate, sodium acetate, sodium citrate, sodium dihydrogen citrate, disodium hydrogen citrate, and sodium hydroxide.
4. 4. The method for synthesizing ferric sodium pyrophosphate positive electrode material using ferric phosphate according to claim 1 or 2, wherein the phosphorus source in step 1 is at least one of phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, sodium pyrophosphate, trisodium dihydrogen pyrophosphate, disodium dihydrogen pyrophosphate, and trisodium dihydrogen pyrophosphate.
5. 5. The method for synthesizing sodium ferric pyrophosphate positive electrode material using ferric phosphate according to claim 1, wherein the spray drying temperature in step 3 is 130-220 ℃, and the feed rate is 0.5% -20%.
6. 6. The method for synthesizing sodium ferric pyrophosphate positive electrode material by utilizing ferric phosphate according to claim 1 or 4, wherein the inert atmosphere in the step 4 is one of argon and nitrogen, and the sintering temperature is 450-600 ℃ and the sintering time is 5-12 h.
7. 7. A sodium ferric phosphate cathode material synthesized by the method according to any one of claims 1-6, wherein the sodium ferric phosphate cathode material is applied to the field of sodium ion batteries.

Description

Method for synthesizing ferric sodium pyrophosphate cathode material by utilizing ferric phosphate Technical Field The invention belongs to the technical field of sodium ion battery anode materials, and particularly relates to a method for synthesizing sodium ferric pyrophosphate anode materials by utilizing ferric phosphate. Background Sodium ion batteries are considered to be the most potential lithium ion battery alternatives due to the abundance of sodium resources, low cost, and higher safety performance. In recent years, great efforts have been made to develop key technologies such as positive electrode materials, negative electrode materials, electrolytes and the like of sodium ion batteries. However, the development of the positive electrode material of the sodium ion battery is limited due to unavoidable drawbacks such as larger radius of sodium ions and lower standard electrochemical potential. To date, the main studied cathode materials include transition metal oxides, prussian blue-based compounds, and polyanionic compounds. Among the polyanionic cathode materials, the iron-based polyanionic cathode material has better application prospect because of the characteristics of strong structural stability, excellent cycle performance, low price, good safety and the like. The NaFePO 4 synthesized by the common solid-phase or liquid-phase method is an electrochemically inert ferrophosphorus ore structure, and the structure has no sodium ion diffusion channel and cannot be used as a battery anode material. The LiFePO 4 is subjected to lithium removal and sodium intercalation by an electrochemical method, so that NaFePO 4 with an olivine structure can be synthesized, but the future development and application of the LiFePO 4 are limited due to the complex synthesis process. In recent years, sodium iron pyrophosphate Na 4Fe3(PO4)2(P2O7) is an electrochemically active iron-based polyanion type positive electrode material which is proved to be suitable for a large-scale energy storage system due to the fact that the theoretical specific capacity is high (128.9 mAh g -1), the raw material cost is low, the raw material is easy to obtain, the synthesis process is simple, and the cycle performance is good. However, the sodium iron phosphate is very easy to be accompanied with electrochemically inert sodium iron phosphate ore type NaFePO 4 in the synthesis process, and the content of the sodium iron phosphate ore type NaFePO 4 directly influences the electrochemical properties of the sodium iron phosphate anode material such as circulation, multiplying power, polarization and the like. Therefore, developing high-purity, low-cost sodium ferric pyrophosphate Na 4Fe3(PO4)2(P2O7) becomes one of the keys for sodium ion battery cathode material research. Commercial ferric phosphate is used as a key precursor in the lithium iron phosphate synthesis process, and has the advantages of stable structure, economy, high atom utilization rate, large-scale production and the like. With the rapid development of new energy automobile industry, the demand of lithium iron phosphate batteries is rapidly growing, and the recycling of waste lithium iron phosphate batteries is also an important problem. Typically, recovery of 1 ton of spent lithium iron phosphate will produce more than 1.5 tons of wet lithium iron phosphate residue. Although there have been a great deal of research reporting the regeneration of lithium iron phosphate from iron phosphate slag, the electrochemical performance of regenerated lithium iron phosphate is significantly inferior to that of commercial lithium iron phosphate. Therefore, the realization of sustainable recycling of the waste lithium iron phosphate battery is of great significance by directly regenerating the iron phosphate slag into valuable materials. Patent CN 115230923A discloses a carbon-coated ferric sodium pyrophosphate positive electrode material, a preparation method and application thereof. And (3) taking commercial iron phosphate or iron phosphate slag of lithium extraction from lithium iron phosphate positive electrode waste powder as a raw material, ball-milling and mixing, and calcining at high temperature to obtain the carbon-coated sodium iron phosphate positive electrode material. The preparation process of the method is simple, however, the sodium ferric phosphate nano powder prepared by the solid phase method is easy to agglomerate, so that the specific surface area of the powder and the utilization rate of electrode materials are relatively low. Patent CN 113060714a discloses a process for preparing Na 4Fe3(PO4)2P2O7 from FePO 4 liquid phase. FePO 4 is used as a raw material, and spherical sodium ferric pyrophosphate is prepared by high-temperature calcination after mixing, wet sanding and spray drying. The method has the characteristics of green, simplicity and convenience and easy amplification. However, long-time sanding can reduce the FePO 4 grain size, but also increase the