(1) A solid-liquid conversion mechanism is proposed to activate the fluorine transport kinetics of iron oxyfluorides enabled by fluoride anion receptor of tris(pentafluorophenyl)borane (TPFPB). TPFPB promotes the dissociation of inert lithium fluoride and provides a facile fluorine transport channel at multiphase interfaces via the formation of solvated F− intermediate therein. The construction of solid-liquid channel with fluorinated cathode electrolyte interface is the key for the achievement of FeO0.3F1.7 and FeO0.7F1.3 in terms of sustaining conversion reaction and high-rate performance. (2) A catalysis effect of Ni nanodomains is proposed to activate the Li-F splitting with much lower dissociation energy and to enable the LiF/Fe/Ni ternary cathode with superior conversion reaction capacity and rate performance. The crowded effect between LiF and dual-metal phases suppresses the growth of crystal grains and promotes the enrichment and penetration of LiF-Fe-Ni triple-phase interfaces. This compact interface contact endows the lithiated fluoride with an ultrahigh initial charge capacity exceeding 600 mAh g− 1 and lowered charge plateau below 3.5 V. (3) We also propose an all-solid-state Li-FeF3 conversion battery reinforced by hierarchical microsphere stacked polymer electrolyte. This gC3N4 stuffed polyethylene oxide (PEO)-based electrolyte is lightweight due to the absence of metal element doping, and it enables the spatial confinement and dissolution suppression of conversion products at soft cathode-polymer interface, as well as Li dendrite inhibition at filler-reinforced anode-polymer interface. All-solid-state Li/FeF3 cells show highly stabilized capacity as high as 300 mAh/g even after 200 cycles and of ~200 mAh/g at extremely high rate of 5 C, as well as ultra-long cycling for at least 1200 cycles at 1 C. (4) For fluoride-garnet solid-state batteries, we propose a simple strategy of interfacial gas release and detergency to smartly convert Li₂CO₃ passivation layer into ion-conductive Li₃PO₄ domains at mild temperature (~ 200^oC). The in-situ formation of PH₃ vapor and its phosphorization enables a dramatic decrease of Li/garnet interfacial resistance down to 2 Ω cm² at room temperature. The prototype of Fe/Cu based fluoride-garnet conversion batteries are successfully driven as rechargeable system with high conversion capacity (400~500 mAh/g) and high-rate performance (251.2 mAh/g at 3 C).

Chilin Li

Appearances