Novel Synthesis of Anhydrous and Hydroxylated CuF₂ Nanoparticles and Their Potential for Lithium Ion Batteries

Abstract

Anhydrous nanoscopic CuF is synthesized from alkoxides Cu(OR) (R=Me, tBu) by their reaction either in pure liquid HF at -70 °C, or under solvothermal conditions at 150 °C using excess HF and THF as solvent. Depending on the synthesis method, nanoparticles of sizes between 10 and 100 nm are obtained. The compound is highly hygroscopic and forms different hydrolysis products under moist air, namely CuF ⋅2 H O, Cu (OH)F , and Cu(OH)F, of which only the latter is stable at room temperature. CuF exhibits an electrochemical plateau at a potential of ≈2.7 V when cycled versus Li in half cell Li-ion batteries, which is attributed to a non-reversible conversion mechanism. The cell capacity in the first cycle depends on the particle size, being 468 mAh g for ≈8 nm crystallite diameter, and 353 mAh g for ≈12 nm crystallite diameter, referred to CuF . However, such a high capacity cannot be sustained for several cycles and the capacity rapidly fades out. The cell voltage decreases to ≈2.0 V for CuF ⋅2 H O, Cu (OH)F , and Cu(OH)F. As all the compounds studied in this work show irreversible conversion reactions, it can be concluded that copper-based fluorides are unsuitable for Li-ion battery applications.

Atomic Doping and Anion Reconstructed CoF2 Electrocatalyst for Oxygen Evolution Reaction

“…[ 16,17 ] Meanwhile, nonnoble metal compounds, for instance, transition metal oxides, [ 18–21 ] perovskite, [ 22,23 ] hydroxide, [ 24,25 ] nitrides, [ 26,27 ] borates, [ 28,29 ] and so on, have also captured extensive interests for preparing high‐efficient OER catalysts. Among them, the metal fluoride, mostly literature reported for supercapacitor, lithium ion battery, etc., [ 30–33 ] is rarely wielded in the field of water electrolysis, possibly due to the chemical/electrochemical instability of fluoride ions and the weak bond between the metal ions and fluoride ions. Actually, fluoride ions can be easily replaced by other anions during the testing process, which is beneficial to optimize the catalytic activity by anionic reconstruction.…”

Lithium fluoride/iron difluoride composite prepared by a fluorolytic sol–gel method: Its electrochemical behavior and charge–discharge mechanism as a cathode material for lithium secondary batteries

“…Although the fluorolytic sol-gel method is commonly used for the preparation of metal fluoride nanoparticles for catalytic and optical applications, offering the advantage of a large reactive surface, [39,40] it has also been applied to the production of battery electrode materials, albeit limitedly. [41][42][43][44] The LiF/FeF2 composite powder prepared in the present study was characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and nitrogen adsorption analysis. Its reaction mechanism was also analyzed by XRD, transmission electron microscopy (TEM), and X-ray absorption spectroscopy (XAS).…”

Li-free Cathode Materials for High Energy Density Lithium Batteries

“…70 Wang et al reported that the formation of Fe is crucial for mitigating the voltage hysteresis of FeF 3 due to the formation of a good electron transport pathway in the insulating LiF matrix. 71 Note that RuO 2 also presents high Cycling performance of (A) S (reproduced from Lv et al 49 ), (B) FeF 3 (reproduced from Fu et al 53 ), (C) CuF 2 (reproduced from Krahl et al 59 ), and (D) MnO 2 (reproduced from Zang et al 58 ).…”