Ultra-Stable, Ultra-Long-Lifespan and Ultra-High-Rate Na-ion Batteries Using Small-Molecule Organic Cathodes

Abstract

Molecule-aggregation organic electrodes in principle possess the “single-molecule-energy-storage” capability for metal-ion rechargeable batteries. Besides dissolution issue, the effect of possible solvent co-intercalation in liquid electrolytes also devalues the true performance of organic electrodes due to the weak Van der Waals forces among organic molecules. Herein, a small-molecule organic cathode called [N,N’-bis(2-anthraquinone)]-perylene-3,4,9,10-tetracarboxydiimide (PTCDI-DAQ, 200 mAh g−1) can deliver the unprecedented results in sodium-ion batteries (SIBs) by carefully choosing high-concentration electrolytes, which can offer more free sodium ions and decrease the solvent co-intercalation effect. Consequently, PTCDI-DAQ can deliver an ultra-stable capacity above 153 mAh g−1 during a long-lifetime operation test in half cells (10 months at least). In full cells, the resulting PTCDI-DAQ II Na3Bi SIBs can deliver a peak discharge capacity of 206 mAh g−1cathode with an average voltage of 1.2 V, running with no capacity decay over 4 months. Meanwhile, our PTCDI-DAQ II Na3Bi SIBs can re-store a world record of 70% capacity retention (142 mAh g−1cathode) at 20 A g−1cathode (100 C). To the best of our knowledge, PTCDI-DAQ can currently represent the best organic cathode for SIBs in the world; and the integrated performance of our PTCDI-DAQ II Na3Bi SIBs can compete with the best SIBs reported to date.