A nanoarchitectured Na6Fe5(SO4)8/CNTs cathode for building a low-cost 3.6 V sodium-ion full battery with superior sodium storage

A novel high-voltage cathode material Na₆Fe₅(SO₄)₈ (NFS) is successfully prepared for sodium-ion batteries for the first time. It is found that the NFS cathode shows a high working voltage of 3.7 V, together with an attractive energy density approaching 450 W h kg⁻¹. And, based on an NFS@5%CNTs cathode and hard carbon (HC) anode, a full NFS@5%CNTs//HC cell can deliver an impressive energy density approaching 350 W h kg⁻¹ and excellent cycling stability over 1000 cycles at 2C.