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)3OK 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)3OK to C6H2(NO2Li2)3OK stabilizes oxidized [C6]n+ to achieve a stable conjugated structure through electron delocalization from −NO2 to [C6]n+. The ordered layer structure C6H2(NO2)3OK can provide large spatial pore channels for Li-ion transport, achieving a high ion diffusion coefficient of 3.41 × 10–6 cm2 s–1.