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.