Iron-based fluorides of tetragonal tungsten bronze structure as potential cathodes for Na-ion batteries

A iron-based fluoride of tetragonal tungsten bronze structure prepared by topotactically densifying a HTB framework is used as a cathode for Na-ion batteries. K-ion stuffing enables the pristine fluoride to achieve an initial charge capacity of 125 mA h g ⁻¹ and reversible capacity of 100–150 mA h g ⁻¹ .