Trinitroaromatic Salts as High-Energy-Density Organic Cathode Materials for Li-Ion Batteries.

Even though organic molecules with designed structures can be assembled into high-capacity electrode materials, only limited functional groups such as -C═O and -C═N- could be designed as high-voltage cathode materials with enough high capacity. Here, we propose a common chemical raw material, trinitroaromatic salt, to have promising potential to develop organic cathode materials with high discharge voltage and capacity through a strong delocalization effect between -NO 2 and aromatic ring. Our first-principles calculations show that electrochemical reactions of trinitroaromatic potassium salt C 6 H 2 (NO 2 ) 3 OK are a 6-electron charge-transfer process, providing a high discharge capacity of 606 mAh g -1 and two voltage plateaus of 2.40 and 1.97 V. Electronic structure analysis indicates that the discharge process from C 6 H 2 (NO 2 ) 3 OK to C 6 H 2 (NO 2 Li 2 ) 3 OK stabilizes oxidized [C 6 ] n + to achieve a stable conjugated structure through electron delocalization from -NO 2 to [C 6 ] n + . The ordered layer structure C 6 H 2 (NO 2 ) 3 OK can provide large spatial pore channels for Li-ion transport, achieving a high ion diffusion coefficient of 3.41 × 10 -6 cm 2 s -1 .