Topochemical Bottom-Up Synthesis of 2D- and 3D-Sodium Iron Fluoride Frameworks

Abstract

ter.8b04010. Experimental details, Mossbauer, FTIR, FESEM, TGA, additional electrochemical, and XRD data, Na-ion channels in the weberite phase, cavity size in the 1D precursor, tables for the structural details, and Mossbauer analysis (PDF)

Fluorinated Materials as Positive Electrodes for Li- and Na-Ion Batteries

“…The orthorhombic Imma Na 2 Fe 2 F 7 was synthesized by a solvothermal route previously used for NaFeF 4 , but the temperature was increased to 230 °C. With regard to theory, the cycling electrochemical properties with sodium are disappointing with an almost constant capacity of 50 mAh g –1 after 50 cycles . But recently, a trigonal T-Na 2 Fe 2 F 7 ( P 3 1 21) prepared from a mixture of NaF, FeF 2 and FeF 3 at 650 °C under Ar showed, in NIB configuration, a high capacity close to the theoretical capacity of 134 mAh g –1 , without any phase transition and very low volume variation (Figure ).…”

“…With regard to theory, the cycling electrochemical properties with sodium are disappointing with an almost constant capacity of 50 mAh g −1 after 50 cycles. 92 But recently, a trigonal T-Na 2 Fe 2 F 7 (P3 1 21) prepared from a mixture of NaF, FeF 2 and FeF 3 at 650 °C under Ar showed, in NIB configuration, a high capacity close to the theoretical capacity of 134 mAh g −1 , without any phase transition and very low volume variation (Figure 25). Over 88% of the initial capacity is still achievable after 1000 cycles.…”

“…NaFeF 4 was also obtained by solvothermal synthesis from a mixture of NaF and FeF 3 (H 2 O) 2 ·H 2 O in tetraethylene glycol (TEG) heated at 180 °C for 24 h. The performances were poor with a capacity of 12 mAh g –1 …”

Polymorphism in Weberite Na2Fe2F7 and its Effects on Electrochemical Properties as a Na-Ion Cathode

“…Weberite-type sodium transition metal fluorides have been studied for their magnetic properties since the 1970s , but have only been explored as Na-ion battery electrode materials over the past few years. − ,, In 2019, Euchner et al predicted, using first-principles calculations, that this material class should lead to good Na-ion diffusion properties, high Na insertion potentials, and high capacities, resulting in energy densities competitive with those of common Li-ion cathode materials . A recent experimental report by Park et al demonstrated exceptional performance for the Na 2 Fe 2 F 7 weberite cathode, including an initial capacity of 184 mAh/g at C/20 and an outstanding full cell capacity retention of 88.3% at 2C (initial capacity of 118 mAh/g) after 1000 cycles .…”

Optimized Structural Dimensionality of CuSbS2as an Anode Material in Sodium-Ion Batteries

“…Additionally, alloying type anodes exhibiting lower voltages are preferred for full cells with high working potential . Recent reports on Sb and Sn/C clearly exemplified even lower working potential in SIBs as compared to LIBs. − Also, the favorable reaction kinetics of the alloying reaction advances low hysteresis, which is of utmost need to make full utilization of charged energy . In addition to the alloying mechanism, the conversion mechanism is also known for SIBs.…”