Prussian blue microcubes-derived FeF3 cathodes for high-energy and ultra-stable lithium and lithium-ion batteries.

Iron trifluoride (FeF 3) is highlighted as a competitive cathode for next-generation lithium and lithium-ion batteries with higher energy densities and lower cost. However, the FeF 3 cathode is typically hindered by rapid capacity fade for their poor electronic/ionic conductivity and unstable electrode/electrolyte interphase. Herein, a microcubic FeF 3 @C composite, where the nanosized FeF 3 particles (<40 nm) are encapsulated by graphitized carbon and linked through surrounding amorphous carbon matrix, is firstly synthesized through the Prussian blue microcubes. When using as the cathode of coin-type lithium batteries, it can achieve stable and ultralong lifespan (over 1000 cycles) at FeF 3 mass loading of ∼2 mg cm−2, ascribing to the compact and thick wrapping of carbon shell and stable cathode solid electrolyte interphase (CEI) during cycling. Besides, the FeF 3 –Li pouch cell, FeF 3 full batteries with pre-lithiated Li 4 Ti 5 O 12 (PLLTO) and pre-lithiated mesocarbon microbeads (PLMCMB) anodes are successfully constructed. To interpret the capacity rising of as-prepared FeF 3 cathodes within initial cycles, the detailed electrochemical behaviors and electrode kinetics are investigated. The results show that the decay of the high-potential decomposition process cannot catch up with the activation of the low-potential conversion reaction The repeated electrochemical activation within initial cycles causes multiple interface and increased Li+ diffusion coefficient (resulted from the amorphization of FeF 3 particle), which induce the capacity rising. [Display omitted] • A microcubic FeF 3 @C composite was synthesized from the Prussian blue microcubes. • As-fabricated FeF 3 cathodes can realize ultra-long cycle performance at ∼2 mg cm−2 • The FeF 3 cathodes were successfully applied in pouch cell and full cell. • Rising capacity within initial cycles is resulted from the amorphization of FeF 3. • Amorphization of FeF 3 leads to the increasing Li+ diffusivity and improved kinetics. [ABSTRACT FROM AUTHOR]