Self-templated fabrication of micro/nano structured iron fluoride for high-performance lithium-ion batteries

Hexagonal-tungsten-bronze-type (abbreviated as HTB) FeF₃·0.33H₂O has been recognized as a promising high-rate cathode material for lithium-ion batteries. However, rational engineering of advanced structures is highly desirable yet challenging to activate the insulating FeF₃·0.33H₂O in practical application. For the first time, a facile and economical solvothermal strategy is demonstrated to synthesize micro/nanostructured FeF₃·0.33H₂O through the self-templated morphology evolution and topotactic phase transformation of commercial FeF₃·3H₂O precursor. Benefiting from the hierarchical structure, the as-prepared FeF₃·0.33H₂O exhibits enhanced rate capability and cycle stability compared with the bulk FeF₃·0.33H₂O obtained through traditional heat treatment of FeF₃·3H₂O. More interestingly, simple adjustment of the synthesis solvent or temperature enables the fabrication of several iron-based fluorides with uniquely hierarchical morphology, which are still hard to be synthesized under the existing methods.