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]^<i>n</i>+ to achieve a stable conjugated structure through electron delocalization from −NO₂ to [C₆]^<i>n</i>+. 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.