Reaching the full capacity of the electrode material Li3FeF6 by decreasing the particle size to nanoscale

Study of sodium manganese fluorides as positive electrodes for Na-ion batteries

“…Among these, largest attention has been devoted to FeF 3 , which when ball-milled with carbon for 24 h exhibits a reversible capacity of 100 mAh/g and moderate operation potential of 2.2 V, related to the Fe III /Fe II redox couple. Alternatively and following reports of the electrochemical performance of Li 3 FeF 6 cryolite in lithium cells [17], isostructural Na 3 FeF 6 was tested in sodium cells and found to exhibit a reversible capacity of 110 mAh/g on the 1st cycle with 0.7 V vs Na°operation potential but with the electrochemical profile showing high polarization and low cyclability, which was attributed to the insulating character of fluorides [18]. In this case, the redox process proceeds through a conversion reaction, which involves important structural reorganization and crucial issues for practical implementation, such as large potential hysteresis between reduction and oxidation [6,19].…”

Metal Fluorides as Lithium-Ion Battery Materials: An Atomic Layer Deposition Perspective

“…Due to the work on primary batteries pure fluorides are generally considered only as conversion cathodes but some reports on intercalation fluorides have been published [41][42][43]. For example, Li 3 FeF 6 has been reported to show intercalation of 0.7-1 Li + ions per fluoride unit in a carbon nanocomposite form, resulting in a reversible capacity of 100-140 mAh/g [41,42]. The capacity depends on the size of the Li 3 FeF 6 particles, with smaller particles resulting in a higher capacity [42].…”

“…For example, Li 3 FeF 6 has been reported to show intercalation of 0.7-1 Li + ions per fluoride unit in a carbon nanocomposite form, resulting in a reversible capacity of 100-140 mAh/g [41,42]. The capacity depends on the size of the Li 3 FeF 6 particles, with smaller particles resulting in a higher capacity [42]. A deeper discharge of the material was reported to lead to LiF formation, indicating a conversion reaction at low potentials.…”

Electrochemical characterization of monoclinic and orthorhombic Li3CrF6 as positive electrodes in lithium-ion batteries synthesized by a sol–gel process with environmentally benign chemicals

“…Lithium transition metal fluorides can be synthesized by solid-state reaction or by gas phase fluorination [3]. An alternative synthesis route for nano-scale lithium transition metal fluorides is a wet chemical precipitation route with HF as fluorine source [4,5]. In general, these syntheses are based on toxic chemicals like HF, LiF or F 2 .…”