Scalable Synthesis of the Na<sub>2</sub>FePO<sub>4</sub>F Cathode Through an Economical and Reliable Approach for Sodium-Ion Batteries
Huangxu Li, Taosheng Wang, Sha Wang, Xu Wang, Yangyang Xie, Junxian Hu, Yanqing Lai, Zhian Zhang
Abstract
Iron-based phosphates have attracted considerable attention as cathode materials for sodium-ion batteries by virtue of their natural abundance, low cost, and nontoxicity. A significant challenge of iron-based phosphates for practical application is the lack of suitable methods for mass production of cathode materials with reliable sodium storage properties. Here, we propose a scalable, economical, and green method to successfully synthesize a sodium iron fluorophosphate (Na2FePO4F) cathode material. Experiments show that pure commercialized FePO4 can be used as a precursor to react with Na salts to obtain the Na2FePO4F/carbon material (NFPF/C). Besides, the rGO-coated FePO4 (FePO4/rGO) precursor can also lead to the successful formation of the Na2FePO4F/C/rGO (NFPF/C/rGO) composite. These results indicate that modification of FePO4 does no harm to the formation of Na2FePO4F, and this feature provides great possibility for tuning the electrochemical performance of Na2FePO4F by controlling the physiochemical properties of FePO4, such as morphology and nanostructures. The features of the as-synthesized materials are well characterized, and the electrochemical performance and kinetics are also studied. NFPF/C/rGO exhibits an enhanced reversible capacity of 118 mA h g–1 at 0.1 C, good high-rate capability, and fast-charging properties. We believe that this method is important and informative for the mass production of cathode materials with reliable sodium storage properties for large-scale energy storage.