High‐Performance Rechargeable Aluminum‐Ion Batteries Enabled by Composite FeF₃ @ Expanded Graphite Cathode and Carbon Nanotube‐Modified Separator

Abstract

Rechargeable aluminum ion batteries (AIBs) are one of the most promising battery technologies for future large‐scale energy storage due to their high theoretical volumetric capacity, low‐cost, and high safety. However, the low capacity of the intercalation‐type cathode materials reduces the competitiveness of AIBs in practical applications. Herein, a conversion‐type FeF3‐expanded graphite (EG) composite is synthesized as a novel cathode material for AIBs with good conductivity and cycle stability. Combined with the introduction of a single‐wall carbon nanotube modified separator, the shuttle effect of the intermediate product, FeCl2, is significantly restrained. Moreover, enhanced coulombic efficiency and reversible capacity are achieved. The AIB exhibits a satisfying reversible specific capacity of 266 mAh g−1 at 60 mA g−1 after 200 cycles, and good Coulombic efficiency of nearly 100% after 400 cycles at a current density of 100 mA g−1. Ex situ X‐ray diffraction and X‐ray photoelectron spectroscopy are applied to explore the energy storage mechanism of FeF3 in AIBs. The results reveal that the intercalation of Al3+ species and the reduction of Fe3+ species occurrs in the discharge process. These findings are meaningful for the fundamental understanding of the FeF3 cathode for AIBs and provide unprecedented insight into novel conversion type cathode materials for AIBs.

2023 Roadmap on molecular modelling of electrochemical energy materials

“…Although multi-valent metals (i.e. Zn, Al) have achieved much longer cycle life than alkali metals [35,36], it lacks a good understanding on their exact working mechanisms during the charge/discharge process and why they behave differently from alkali metals.…”

Toward High Energy Density FeFx (x=2 and 3) Cathodes for Lithium‐Ion Batteries

“…Various recent studies have reported the application of conductive matrix materials in FeF x cathodes. Wherein, carbon‐based FeF x composites have been the preferred method to optimize the electrochemical properties of FeF x cathodes [87,88] . Carbon materials have tunable structures and excellent mechanical stability, providing sufficient active sites and promoting interfacial ion diffusion.…”

“…Wherein, carbonbased FeF x composites have been the preferred method to optimize the electrochemical properties of FeF x cathodes. [87,88] Carbon materials have tunable structures and excellent mechanical stability, providing sufficient active sites and promoting interfacial ion diffusion. It plays a crucial role in the electron/ion transport and structural stability of FeF x cathodes.…”

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

“…Typically, liquid-phase synthesis, including chemical precipitation, [60] hydrothermal, [61] solvothermal, [62,63] sol-gel, [64] and thermal decomposition methods [65] based on different fluorine sources, (hydrogen fluoride (HF) solution, [66] NH 4 F, [67] NH 4 HF 2 , [68,69] metal hexafluorosilicate, [70] F-containing ionic liquids (ILs), [71] etc.) has been utilized to prepare nanoparticle MFs, [72] metal oxyfluorides, [73] mixed metal difluorides, [74] and MF-carbon composites.…”