Low Temperature Nanotailoring of Hydrated Compound by Alcohols: FeF₃·3H₂O as an Example. Preparation of Nanosized FeF₃·0.33H₂O Cathode Material for Li-Ion Batteries

Abstract

Iron fluoride is a kind of high-capacity conversion-type cathode material for lithium-ion batteries (LIBs) and shows attractive practical application potential. However, it still faces many challenges, such as poor electronic conductivity and volume change while cycling. Reducing particle size to nanoscale has been proved to be an effective way to address the poor electronic conductivity and huge volume change of iron fluoride cathodes for LIBs. In this study, a low temperature nanotailoring (LTNT) strategy is proposed to realize the conversion of microsized FeF 3 •3H 2 O to nanosized FeF 3 •0.33H 2 O by one-step treating with the assistance of alcohols. Meanwhile, the particle size and morphology of iron fluorides can be controlled by regulating the processing conditions. When evaluated as a cathode material for LIBs, the as-prepared bare FeF 3 •0.33H 2 O shows a high capacity of 190 mAh g −1 after 50 cycles with excellent rate capability. This LTNT method is applicable to hydrates and even can be extended to easily hydrated compounds.

N, S Co‐Doped Porous Carbon from Antibiotic Bacteria Residues Enables a High‐Performance FeF3 ⋅ 0.33H2O Cathode for Li‐Ion Batteries

“…During the charge‐discharge process, FeF 3 ⋅ 0.33H 2 O is lithiated into LiFeF 3 ⋅ 0.33H 2 O (225 mAh g −1 , 4.5–2.0 V), and then LiFeF 3 ⋅ 0.33H 2 O transforms into LiF and Fe ⋅ 0.33H 2 O via a conversion reaction (450 mAh g −1 , 2.0–1.0 V) [8,9] . However, their practical applications are restricted by the insulation characteristic due to the strong Fe−F ionic bond [10,11] . Fortunately, FeF 3 ⋅ 0.33H 2 O has a special 1D tunnel structure with a little hydration water, which can enhance the electric conductivity (band gap FeF 3 ⋅ 0.33H 2 O 0.95 eV vs. FeF 3 4.318 eV), accelerate Li‐ion transport and stabilize the structure [12–15] .…”

Synthesis, Structure, and Electrochemical Properties of Some Cobalt Oxalates

“…It is noticeable that both I and III exhibited a large discrepancy of the plateaus between charging and discharging, i.e., a large cell polarization. This is due mainly to the insufficient conductivity of the electrode, analogous to some other cathodes. − Meanwhile, the cycling performances were poor in this study, but this may originate from the decomposition and consumption of electrolytes at high voltages. As previously reported, several Co-based polyanions belong to high-voltage cathodes; , therefore, it is necessary to use high-voltage electrolytes to improve cycling performance and unveil the intrinsic cycling stabilities of the studied electrode materials.…”

Nanosized FeF3·0.33H2O as Cathode Material for High-Performance Li-Ion Batteries

“…In addition, HTB (hexagonal tungsten bronze structure)-FeF 3 •0.33H 2 O has a straight 1D tunnel with a stable structure during lithiation. 12 Moreover, FeF 3 •0.33H 2 O is the key precursor to the synthesis of other open framework fluorides (such as K 0.6 FeF 3 ). Despite these advantages, there are still many problems in the manufacture of FeF 3 •0.33H 2 O materials.…”

“…The liquidprecipitate method usually requires an additional ball-milling process to reduce particle size, which obviously increases the time cost. 12 Reducing the grain size can increase the electrochemical reaction activity during the cycling process, shorten the electron transfer path, and reduce volume expansion. 2 Here, a safe solvothermal process with low cost was used to prepare FeF 3 •0.33H 2 O with nanometer size.…”