Stacking Faults Assist Lithium-Ion Conduction in a Halide-Based Superionic Conductor.

In the pursuit of urgently needed, energy dense solid-state batteries for electric vehicle and portable electronics applications, halide solid electrolytes offer a promising path forward with exceptional compatibility against high-voltage oxide electrodes, tunable ionic conductivities, and facile processing. For this family of compounds, synthesis protocols strongly affect cation site disorder and modulate Li mobility. In this work, we reveal the presence of a high concentration of stacking faults in the superionic conductor LiYCl and demonstrate a method of controlling its Li conductivity by tuning the defect concentration with synthesis and heat treatments at select temperatures.

Probing reaction processes and reversibility in Earth-abundant NaFeF for Na-ion batteries.

Sodium (Na)-ion batteries are the most explored 'beyond-Li' battery systems, yet their energy densities are still largely limited by the positive electrode material. NaFeF is a promising Earth-abundant containing electrode and operates through a conversion-type charge-discharge reaction associated with a high theoretical capacity (336 mA h g). In practice, however, only a third of this capacity is achieved during electrochemical cycling.