Microfluidic-Assembled 3D FeF3/rGO Composite Fabric Cathodes with Egg-roll-Like Confinement Structure for High-Rate and Long-Cycle Lithium-Ion Batteries

The relatively low theoretical capacity of conventional cathodes has become one of the key bottlenecks in developing high-energy-density lithium batteries. Iron(III) fluoride (FeF3) cathodes are viable candidates for next-generation energy storage applications by virtue of their elevated theoretical specific capacity derived from conversion-type electrochemistry; nonetheless, their practical realization remains critically impeded by intrinsically poor electronic transport properties and substantial volumetric dilation. Herein, we employed a microfluidic assembly strategy to develop an FeF3/reduced graphene oxide (rGO) composite fabric (FGF) electrode featuring a three-dimensional network structure. In this architecture, rGO sheets are interconnected to form confined spaces that tightly encapsulate FeF3 nanoparticles into egg-roll-like structural fibers, which are further bridged to create a porous network fabric structure. Benefiting from the high conductivity, excellent mechanical strength, and moderate sheet size of rGO sheets, the resulting three-dimensional network structure not only overcomes the low conductivity of FeF3, enabling rapid electron transport, but also effectively suppresses the volume expansion and dissolution-migration of FeF3 particles during charge–discharge processes. Consequently, the as-formed FGF The electrode demonstrated superior electrochemical behavior, maintaining 98% of its initial capacity across the current density range of 0.5–5 A·g–1. Following 1000 charge–discharge cycles at 0.7 A·g–1, the active material preserved a reversible specific capacity of 72 mAh·g–1. This work not only provides an effective strategy for iron fluoride-based conversion cathodes, but also offers insights into the structural regulation of graphene frameworks for high-energy-density lithium–ion batteries, highlighting the critical importance of fluorinated graphene architectures in next-generation cathode design.