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

Abstract

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 .

Advancements in cathode materials for potassium-ion batteries: current landscape, obstacles, and prospects

“…151 Theoretical calculations predict that C 6 H 2 (NO 2 ) 3 OK (potassium picrate) undergoes a 6-electron charge-transfer process, resulting in a high discharge capacity of 606 mA h g À1 . 151 Octahydroxytetraazopentacene, with a theoretical capacity of close to 520 mA h g À1 , has been experimentally reported as a high-capacity organic material. 152 Additionally, bipolar organic molecules like tetrathiafulvalene, which enable reversible insertion/extraction of both anions and K + (e.g., TFSI À , FSI À , PF 6 À , etc.…”

“…An example of such promise ( albeit necessitating caution in handling) appears to lie in trinitroaromatic salts, such as C 6 H 2 (NO 2 ) 3 OK which present as nitro-rich organic cathode materials with elevated discharge capacity and voltage due to the strong delocalisation effect between aromatic rings and –NO 2 . 151 Theoretical calculations predict that C 6 H 2 (NO 2 ) 3 OK (potassium picrate) undergoes a 6-electron charge-transfer process, resulting in a high discharge capacity of 606 mA h g −1 . 151 Octahydroxytetraazopentacene, with a theoretical capacity of close to 520 mA h g −1 , has been experimentally reported as a high-capacity organic material.…”

Tuning Electrochemical Properties of Nitroaromatic Cathodes by Function‐Oriented Design for Rechargeable Lithium‐Ion Batteries

“…[48] While a large family of nitroaromatics has been revealed in our initial disclosure, [45] few nitroaromatics other than DNBs have also been investigated successively by other groups for LIBs. [49,50] For example, Xu et al reported that 1,5-dinitronaphthalene as a naphthalene analogue of DNBs showed an ultrahigh specific capacity of 1338 mAh g −1 through a six-electron reaction though the reaction was not reversible. [51] All these works demonstrate the multielectron transfer capability of the nitro group, thereby rendering nitroaromatic compounds as potential organic cathode materials for next-generation metalion batteries.…”

“…[ 48 ] While a large family of nitroaromatics has been revealed in our initial disclosure, [ 45 ] few nitroaromatics other than DNBs have also been investigated successively by other groups for LIBs. [ 49,50 ] For example, Xu et al. reported that 1,5‐dinitronaphthalene as a naphthalene analogue of DNBs showed an ultrahigh specific capacity of 1338 mAh g −1 through a six‐electron reaction though the reaction was not reversible.…”