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 -NO2 and aromatic ring. Our first-principles calculations show that electrochemical reactions of trinitroaromatic potassium salt C6H2(NO2)(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 C6H2(NO2)(3)OK to C6H2(NO2Li2)(3)OK stabilizes oxidized [C-6](n+) to achieve a stable conjugated structure through electron delocalization from -NO2 to [C-6](n+). The ordered layer structure C6H2(NO2)(3)OK can provide large spatial pore channels for Li-ion transport, achieving a high ion diffusion coefficient of 3.41 x 10(-6) cm(2) s(-1).