Capacity Fading in Li2FeSiO4 Cathode Material: Intrinsic or Extrinsic

Abstract

We report the origin of capacity fading in Li 2 FeSiO 4 cathode material, while addressing the challenges associated with the synthesis of phase-pure Li 2 FeSiO 4 positive electrode materials in bulk and nanostructured geometries. The process has been optimized to remove iron oxide (Fe 2 O 3) impurities and for effective carbon coating on a Li 2 FeSiO 4 nanostructured core using a carbon source precursor during the synthesis process. X-ray diffraction measurements confirm the phase purity and nanocrystalline nature of synthesized materials. UV-visible spectroscopic measurements are carried out to understand the electronic/optical characteristics, and their correlation with materials' electrochemical performance is investigated. The impact of iron charge state in an FeO 4 tetrahedra configuration is correlated to the electrochemical performance together with the lithium-ion transporting states. The Jahn-Teller active FeO 4 tetrahedra may show structural distortion in the sub-lattice of Li 2 FeSiO 4 with different charge states and may be the main source of capacity fading in Li 2 FeSiO 4 cathode material from the first cycle onwards.