In situ construction of oxygen vacancy-rich and fluorine-doped carbon-coated Ca2Fe2O5 for improved lithium storage performance

Abstract

Transition metal oxides (TMOs) have caused great concerns as anode candidates for state-of-the-art lithium-ion batteries (LIBs). However, the intrinsic deficiencies of low electrical conductivity and bulk effect greatly impede their commercial applications. Here, we constructed fluorine-doped and carbon-coated Ca₂Fe₂O₅ complexes (CFO@FC) with abundant oxygen vacancies (O_v) through a one-step calcining treatment using polyvinylidene difluoride (PVDF) as F and carbon sources. Both XPS and EPR results reveal the presence of abundant O_v. The CFO@FC anode exhibits enhanced cycling performance with a specific capacity of 927 mA h g⁻¹ after 400 cycles at 200 mA g⁻¹ for LIBs and superior rate capability. The joint work of in situ formed oxygen vacancy-enriched and carbon coating not only enhances the electronic conductivity and high Li⁺ diffusion co-efficient, but also provides a stable structure with more active sites exposed.