Scalable Synthesis of the Na₂FePO₄F Cathode Through an Economical and Reliable Approach for Sodium-Ion Batteries

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.

Progress on Fe‐Based Polyanionic Oxide Cathodes Materials toward Grid‐Scale Energy Storage for Sodium‐Ion Batteries

“…[208] Based on the pre-modification of FePO 4 did not affect the formation of Na 2 FePO 4 F, Li et al obtained reliable performance NFPF/C and NFPF/C/rGO materials with FePO 4 and FePO 4 /rGO precursors via a simple ball milling process. [209] The result may provide a new idea for modulating the electrochemical performance of Na 2 FePO 4 F by controlling the morphology and nanostructure of the precursor. Liu et al synthesized NFPF-H, NFPF-EG, and NFPF-PEG with different microstructures by hydrothermal reaction and carbon coating process, and then employed them in sodium-ion batteries.…”

“…www.advancedsciencenews.com www.small-methods.com [209] only NaFeSO 4 F showed redox activity toward the metal Li with a redox voltage of 3.6 V, corresponding to the removal of 0.7 Na ions. NaFe 1−x M x SO 4 F (M = Co, Ni, Mn) solid solution phases could be formed, but Na 1−x Li x MSO 4 F (x > 0.4) solid solution phases could not be obtained due to structural sensitivity.…”

Iron‐Phosphate‐Based Cathode Materials for Cost‐Effective Sodium‐Ion Batteries: Development, Challenges, and Prospects

“…The mainstream strategy to improve electronic conductivity is carbon coating. Carbon source or carbon material including glucose, [74] sucrose, [75] citric acid, [76] ascorbic acid, [77] biomass carbon, [78] carbon black, [79] CNT, [80] and rGO [81] etc. have been used to be uniformly coated the surface to enhance the electrical conductivity of the material and maintain structural stability.…”

“…h) Schematic diagram of the synthetic route of rGO modified FePO 4 for Na 2 FePO 4 F. Reproduced with permission. [81] Copyright 2021, American Chemical Society.…”

“…[85] Synthesis Routes: Recently, the impact of raw materials on electrochemical performance of Na 2 FePO 4 F has also aroused attention. Li et al [81] modified the commercial FePO 4 with rGO (Figure 10h), and found that the precoating on FePO 4 precursor would not have negative impact on the successful preparation of Na 2 FePO 4 F. The reversible capacity of the Na 2 FePO 4 F/C/rGO composite cathode at 0.1 C can reach 118 mA h g −1 , and capacity retention of 72% after 350 cycles was obtained. Mesoporous Na 2 FePO 4 F was prepared by means of mesoporous FePO 4 , which effectively inhibits the growth and agglomeration of particles and alleviates the volume effect of charging-discharging process.…”