A Zero-Strain Insertion Cathode Material for Room-Temperature Fluoride-Ion Batteries

Abstract

A fluoride-ion battery (FIB) is a novel type of energy storage system that has a higher volumetric energy density and low cost. However, the high working temperature (>150 °C) and unsatisfactory cycling performance of cathode materials are not favorable for their practical application. Herein, fluoride ion-intercalated CoFe layered double hydroxide (LDH) (CoFe-F LDH) was prepared by a facile co-precipitation approach combined with ion-exchange. The CoFe-F LDH shows a reversible capacity of ∼50 mAh g–1 after 100 cycles at room temperature. Although there is still a big gap between FIBs and lithium-ion batteries, the CoFe-F LDH is superior to most cathode materials for FIBs. Another important advantage of CoFe-F LDH FIBs is that they can work at room temperature, which has been rarely achieved in previous reports. The superior performance stems from the unique topochemical transformation property and small volume change (∼0.82%) of LDH in electrochemical cycles. Such a tiny volume change makes LDH a zero-strain cathode material for FIBs. The 2D diffusion pathways and weak interaction between fluoride ions and host layers facilitate the de/intercalation of fluoride ions, accompanied by the chemical state changes of Co2+/Co3+ and Fe2+/Fe3+ couples. First-principles calculations also reveal a low F– diffusion barrier during the cyclic process. These findings expand the application field of LDH materials and propose a novel avenue for the designs of cathode materials toward room-temperature FIBs.

Fluorine Chemistry in Rechargeable Batteries: Challenges, Progress, and Perspectives

“…Recently, a F – -ion-intercalated CoFe-layered double hydroxide (CoFe-F LDH) was reported as a cathode material for FIBs. Zhang and co-workers prepared the CoFe-F LDH through a facile coprecipitation approach combined with an ion-exchange method (Figure a) and successfully paired this material as a cathode with a Li metal anode in a CsF-based organic liquid electrolyte . The Li||CoFe-F LDH cell delivered a stable specific capacity of 48.9 mAh g –1 during 100 cycles at 10 mA g –1 under room temperature (Figure b) owing to the unique topochemical transformation property and small volume change (∼0.82%) of CoFe-F LDH materials accompanied by electrochemical intercalation/intercalation of F – ions.…”

“…(b) Cycling performance and CE for the cell Li||CoFe-F LDH. Reproduced with permission from ref . Copyright 2022 Wiley-VCH.…”

“…Zhang and co-workers prepared the CoFe-F LDH through a facile coprecipitation approach combined with an ion-exchange method (Figure 25a) and successfully paired this material as a cathode with a Li metal anode in a CsF-based organic liquid electrolyte. 592 The Li||CoFe-F LDH cell delivered a stable specific capacity of 48.9 mAh g −1 during 100 cycles at 10 mA g −1 under room temperature (Figure 25b) owing to the unique topochemical transformation property and small volume change (∼0.82%) of CoFe-F LDH materials accompanied by electrochemical intercalation/intercalation of F − ions. Moreover, the good rate performance of CoFe-F LDH indicated that the mitigation of the F − ion in the layer spacing was facilitated by the weak electrostatic interaction between the anions and the host layers with a low diffusion barrier.…”

High-Capacity and Long-Cycling F-Ion Pouch Cells Enabled by Green Electrolytes

“…The CuF 2 |LE3|Pb cell exhibits outstanding cycling performance and high specific capacity at the highest current density compared with other reported liquid FIBs (Figure D and Table S1). − Note that the dual-ion batteries involving other shuttling ions (e.g., K + , Na + ) apart from F – are not included in the comparison. The ChCl-regulated electrolyte also endows FIBs with superior rate performance.…”