Building an Electronic Bridge via Ag Decoration to Enhance Kinetics of Iron Fluoride Cathode in Lithium-Ion Batteries

As a typical multielectron cathode material for lithium-ion batteries, iron fluoride (FeF₃) and its analogues suffer from poor electronic conductivity and low actual specific capacity. Herein, we introduce Ag nanoparticles by silver mirror reaction into the FeF₃·0.33H₂O cathode to build the electronic bridge between the solid (active materials) and liquid (electrolyte) interface. The crystal structures of as-prepared samples are characterized by X-ray diffraction and Rietveld refinement. Moreover, the density of states of FeF₃·0.33H₂O and FeF₃·0.33H₂O/Ag (Ag-decorated FeF₃·0.33H₂O) samples are calculated using the first principle density functional theory. The FeF₃·0.33H₂O/Ag cathodes exhibit significant enhancements on the electrochemical performance in terms of the cycle performance and rate capability, especially for the Ag-decorated amount of 5%. It achieves an initial capacity of 168.2 mA h g^-1 and retains a discharge capacity of 128.4 mA h g^-1 after 50 cycles in the voltage range of 2.0-4.5 V. It demonstrates that Ag decoration can reduce the band gap, improve electronic conductivity, and elevate intercalation/deintercalation kinetics.