Organic‐Carbon Core–Shell Structure Promotes Cathode Performance for Na‐Ion Batteries.

The organic‐carbon core‐shell structure is constructed for the cathode material of [N,N'‐bis(2‐anthraquinone)]‐perylene‐3,4,9,10‐tetracarboxydiimide (PTCDI‐DAQ, 200 mAh g−1) through an interesting strategy called the surface self‐carbonization. As expected, the organic‐carbon core–shell structure (PTCDI‐DAQ@C) can endow PTCDI‐DAQ the outstanding cathode performance in Na‐ion batteries. In half cells using 1 m NaPF6/DME, PTCDI‐DAQ@C can maintain 173 mAh g−1 for nearly one year, while PTCDI‐DAQ quickly decreases from 203 to 121 mAh g−1 only after 100 cycles. Meanwhile, the constructed Na‐ion full cells with the Na‐intercalated hard carbon anode can deliver the peak discharge capacity of 195 mAh g−1cathode and the high median voltage of 1.7 V in 0.9–3.2 V, corresponding to the peak energy densities of 332 Wh kg−1cathode and 184 Wh kg−1total mass, respectively. Notably, the electrode materials only include the very cheap elements of C, H, O, N, and Na. Furthermore, the Na‐ion full cells can also show the very impressive high‐temperature (197 mAh g−1cathode at 50 °C) and subzero (185/90 mAh g−1cathode at −10/−40 °C) performances, respectively. To the best of the authors' knowledge, the comprehensive properties of the Na‐ion full cells are the best results based on organic cathodes. [ABSTRACT FROM AUTHOR]