Next Generation Positive Electrode Materials Enabled by Nanocomposites: -Metal Fluorides-

Low Temperature Nanotailoring of Hydrated Compound by Alcohols: FeF3·3H2O as an Example. Preparation of Nanosized FeF3·0.33H2O Cathode Material for Li-Ion Batteries

Iron fluoride is a kind of high-capacity conversion-type cathode material for lithium-ion batteries (LIBs) and shows attractive practical application potential. However, it still faces many challenges, such as poor electronic conductivity and volume change while cycling. Reducing particle size to nanoscale has been proved to be an effective way to address the poor electronic conductivity and huge volume change of iron fluoride cathodes for LIBs. In this study, a low temperature nanotailoring (LTNT) strategy is proposed to realize the conversion of microsized FeF₃·3H₂O to nanosized FeF₃·0.33H₂O by one-step treating with the assistance of alcohols. Meanwhile, the particle size and morphology of iron fluorides can be controlled by regulating the processing conditions. When evaluated as a cathode material for LIBs, the as-prepared bare FeF₃·0.33H₂O shows a high capacity of 190 mAh g^-1 after 50 cycles with excellent rate capability. This LTNT method is applicable to hydrates and even can be extended to easily hydrated compounds.

Anchoring Nanostructured Manganese Fluoride on Few-Layer Graphene Nanosheets as Anode for Enhanced Lithium Storage

Manganese fluoride (MnF2)/few-layer graphene nanosheets (GNS) composites are successfully prepared via a facile solvothermal method. It is found that in situ formed tetragonal MnF2 submicron crystals (50-200 nm) with good crystallinity anchoring homogeneously onto conducting GNS, allows the electrically insulating MnF2 particles to be wired up to the current collector with enhanced electron transport pathway. The MnF2/GNS composites act as anode in LIBs and display prominently improved electrochemical performance in comparison to that of pure MnF2, on account of the close interactions between the underlying graphene nanosheets and MnF2 particles grown atop. Distinctly enhanced capacity as high as 489 mAh g(-1) after 100 cycles can be obtained at 600 mA g(-1), while the self-activation process can be greatly accelerated at 6000 mA g(-1) with a maximum specific capacity of 530 mAh g(-1). With long cycling stability for 4000 cycles at 6000 mA g(-1), the MnF2/GNS composite can be deemed as an attractive candidate anode for high-capacity, long cycle life, and environmentally friendly LIBs.