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

Abstract

Fluorine is known to be a key element for various components of batteries since current electrolytes rely on Li-ion salts having fluorinated ions and electrode binders are mainly based on fluorinated polymers. Metal fluorides or mixed anion metal fluorides (mainly oxyfluorides) have also gained a substantial interest as active materials for the electrode redox reactions. In this review, metal fluorides for cathodes are considered; they are listed according to the dimensionality of the metal fluoride subnetwork. The synthesis conditions and the crystal structures are described; the electrochemical properties are briefly indicated, and the nature of the electron transport agent is noted. We stress the crucial importance of the elaboration processes to induce the presence of cation disorders, of anion substitutions (mainly F–/O2– or F–/OH–) or vacancies. Finally, we show that an accurate structural characterization is a key step to enable enhanced material performances to overcome several lasting roadblocks, namely the large irreversible capacity and poor energy efficiency that are frequently encountered.

Metal Fluoride Cathode Materials for Lithium Rechargeable Batteries: Focus on Iron Fluorides

“…[83] The performance of the 3D FeF 3 •0.33H 2 O nanostructure delivered a high capacity of 172 mAh g −1 at 0.1 C. To further explore the structure prototypes for improving the electrochemical performance, pyrochlore phase iron fluorides (FeF 3 •0.5H 2 O) were synthesized by Li et al (Figure 9b). [96] Pyrochlore-type FeF 3 •0.5H 2 O with a larger molecular volume (V m ) (≈69 Å 3 ) [96,196] than dense structured ReO 3 -type FeF 3 (≈52 Å 3 ) [41,197] and HTB-type FeF 3 •0.33H 2 O (≈59 Å 3 ) [198] with 1D single ion channels, exhibited interconnected 3D ion channels, suggesting an excellent cation insertion ability. Compared with the 1D channels of the HTB phase, the pyrochlore phase with more tightly confined H 2 O molecules in zigzag channels showed a higher storage performance.…”

“…Unlike the dense structure of FeF 3 , the open ion channels in FeF 3 hydrates facilitate the diffusion of Li + and improve the intrinsic conductivity, which favors the solid‐solution behavior derived from the Li insertion mechanism. There were several main structures of FeF 3 with trace hydration, such as some mineral phases (hexagonal tungsten bronze (HTB) (FeF 3 ·0.33H 2 O), [ 195 ] and pyrochlore (FeF 3 ·0.5H 2 O) [ 196 ] ), all of which are characterized by FeF 6 octahedra connected by corner sharing to form a special hexagonal cavity centered on water molecules. Due to all the O–F distances in the large hexagonal cavities (over 3 Å), FeF 3 ·0.33H 2 O, with a 1D tunnel, has rapid Li + transportation.…”

“…(Figure 9b). [ 96 ] Pyrochlore‐type FeF 3 ·0.5H 2 O with a larger molecular volume ( V m ) (≈69 Å 3 ) [ 96,196 ] than dense structured ReO 3 ‐type FeF 3 (≈52 Å 3 ) [ 41,197 ] and HTB‐type FeF 3 ·0.33H 2 O (≈59 Å 3 ) [ 198 ] with 1D single ion channels, exhibited interconnected 3D ion channels, suggesting an excellent cation insertion ability. Compared with the 1D channels of the HTB phase, the pyrochlore phase with more tightly confined H 2 O molecules in zigzag channels showed a higher storage performance.…”

The Progress of Hard Carbon as an Anode Material in Sodium-Ion Batteries

“…Anode materials play an important role in facilitating sodium-ion batteries with outstanding electrochemical performance. The design of novel anode materials with excellent performance and low cost can accelerate the commercialization of sodium-ion batteries [ 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 ]. Among the many anode electrode materials of sodium-ion batteries, hard carbon materials have the superiority of high capacity, low price, and low working voltage, and their unique structure is conducive to sodium-ion adsorption and reversible embedding/removal, showing excellent sodium storage performance, making them the most likely anode materials to be commercialized [ 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 ].…”

Trifluoromethylated 4,5-Dihydro-1,2,4-triazin-6(1H)-ones via (3+3)-Annulation of Nitrile Imines with α-Amino Esters

“…The functionalization of organic molecules with fluorine atom(s) and/or with fluoroalkyl groups has been recognized as an efficient method for the tuning of their physico-chemical behavior and biological activity [ 1 , 2 , 3 , 4 ]. The introduction of fluorine atoms into the parent non-fluorinated compound enables control on properties such as the metabolic stability, reactivity, acidity, oleophilicity, and conformational effects, among others, which are of general significance for the search of new advanced materials [ 5 , 6 , 7 ], and compounds of potential medicinal [ 8 , 9 , 10 ] and agrochemical applications [ 11 ]. For this reason, the development of new, efficient synthetic methods leading to fluorinated products, in particular, fluoromethylated N -heterocycles [ 12 , 13 , 14 ], is highly desirable.…”