High-Performance LiF@C-Coated FeF₃·0.33H₂O Lithium-Ion Batteries with an Ionic Liquid Electrolyte

Abstract

A new lithium-ion battery cathode material of LiF@C-coated FeF 3 ·0.33H 2 O of 20 nm primary particles and 200–500 nm secondary particles is synthesized. The redox reaction mechanisms of the new cathode material and the influence of different electrolytes on the electrochemical performance of LiF@C-coated FeF 3 ·0.33H 2 O are investigated. We show that LiF@C-coated FeF 3 ·0.33H 2 O using a LiFSI/Pyr 1,3 FSI ionic liquid electrolyte exhibits high reversible capacities of 330.2 and 147.6 mAh g –1 at 200 and 3600 mA g –1 , respectively, as well as maintains high capacity over cycling. Electrochemical characterization shows that the high performance is attributed to higher electronic conductivity of the coating, continuous compensation of the loss of LiF product through the coating, higher ionic conductivity of both the coating and the electrolyte, and higher stability of the electrolyte.

Graphitized Carbon-Coated Iron Fluoride Nanocavities for Enhanced Kinetics of Multielectron Cathode Conversion Reactions

“…where m B is the mass of FeF 3 /GC composite cathodes, M B is the molar mass, V M is the molar volume, S is the contact area between the electrode and the electrolyte, ΔE s is the I R drop, and ΔE τ is the potential difference. 57 It is vividly illustrated in Figure 5b that all three samples have similar Li + diffusion coefficients during discharge with each at 2.27 × 10 −11 , 2.92 × 10 −11 , and 2.36 × 10 −11 cm 2 s −1 , respectively. Furthermore, the FF-800 cathode generally shows a D Li + higher than those of the FF-700 and FF-900 cathodes, accounting for the comparative superiority of the FF-800 cathode.…”

“…Moreover, the D Li + can be determined by measuring the potential change at the working and counter cathodes under a fixed pulse current . Based on the GITT data in Figure a, the D Li + of three cathodes can be obtained using the following calculation formula: where m B is the mass of FeF 3 /GC composite cathodes, M B is the molar mass, V M is the molar volume, S is the contact area between the electrode and the electrolyte, Δ E s is the I R drop, and Δ E τ is the potential difference …”

From Amorphous to Crystalline Thin-Film FeF3 Conversion Electrodes by Sputtering Deposition

“…The same peak can be observed for FeF 3 deposited at 400 °C using grazing-angle XRD with 0.268° incident angles. The peak at 2θ = 24.2° corresponds to the (012) crystallographic orientation of crystalline FeF 3 . ,, For FeF 3 deposited at 250 °C and below, no noticeable peaks are observed, suggesting the amorphous nature of the film. The morphologies of the FeF 3 thin films developed at various temperatures are characterized by SEM, as shown in Figure c.…”

“…At 150 °C, small grain sizes of FeF 3 started to form, but clearly, for deposition temperatures above 400 °C, the major crystalline form of FeF 3 rhombohedral crystallites was formed. The estimated grain sizes were about 50–80, 300–400, and 400–500 nm for FeF 3 prepared at 150, 400, and 600 °C, respectively. , Moreover, X-ray reflectometry (XRR) was adopted to determine the density of the FeF 3 thin films (black curve in Figure b). The XRR curves were fit using Gen-X simulation (Figure S3, in the Supporting Information), where the density of the films increases with the deposition temperature.…”

Ionic Liquids Endowed with Novel Hybrid Anions for Supercapacitors

“…Ionic liquids (ILs), as a state-of-the-art kind of ambient temperature molten salt, have captured intensive insights because of their green characteristic. Close attention to the ILs has been widely paid in various aspects, such as electrolytes, − energy applications, − catalytic reactions, , material modifications, , and efficient gas absorbents. − Compared with the traditional organic electrolytes, they are considered to be more secure because of their negligible vapor pressure, high thermal stability, and nonflammability, which have therefore been considered as a substitute for organic electrolytes in EDLCs. The cations and anions do not match in terms of size and tend to exhibit some degree of charge delocalization due to the weak interaction between the constituent ions, which is usually responsible for their high ionic conductivity.…”