Reversible Multi-Electron Transfer of Cr 2.8+ /Cr 4.4+ in O3-Type Layered Na 0.66 Fe 1/3 Cr 1/3 Ti 1/3 O 2 for Sodium-Ion Batteries

Abstract

© The Author(s) 2018. Na-deficient O3-type Na 0.66 Fe 1/3 Cr 1/3 Ti 1/3 O 2 material is synthesized by a simple solid-state reaction and its electrochemical property as a cathode material for sodium ion battery is evaluated for the first time. It delivers an initial large discharge capacity of 135.5 mA h g −1 in the voltage range of 1.5–4.1 V at 0.1C with a smooth discharge voltage profile. X-ray absorption technique indicates that the redox processes occur entirely at the chromium sites during the Na ion intercalation and deintercalation, while Ti 4+ and Fe 3+ remain as stabilizing spectators in layered Na 0.66 Fe 1/3 Cr 1/3 Ti 1/3 O 2. Our results have demonstrated the new pathway to realize multi-electron transfer of Cr 2 +∼3 + /Cr 4.4+ redox in layered compounds.