"Nitrated Organic Crystals as Electrochemical Reaction Sites for High-Capacity Lithium Batteries" 

Ethan Binkley, MSE PhD Candidate 

Advisor(s): Prof. Steve Son, Prof. Jian Xie

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ABSTRACT

Organic based nitro (-NO2) group containing materials have recently shown promising performance as lithium battery cathode materials utilizing Li intercalation and amine reduction of the -NO2 groups present on the molecules. The combination of the extraction of both electrochemical and thermochemical energy from these materials offers exciting opportunities in many unique power applications. Based off the electrochemical reaction pathways presented in previous work on nitroaromatic materials (nitronapthalenes and nitrobenzenes), our candidate nitrated materials of trinitrotoluene (TNT) and 1,3,5-trinitro-1,3,5-triazine (RDX) have high electrochemical theoretical capacities of ~710 mAh/g. After an initial optimization of binder for our -NO2 containing materials, we found that polyvinylidene fluoride (PVDF) is one of the better binders for performance and offers a more consistent and uniform slurry cast. We demonstrate an approximately 25% reversible maximum capacity of 460 mAh/g for TNT and an irreversible 265 mAh/g for RDX utilizing a Li-bis(trifluoromethanesulfonyl)imide (LiTFSI) based electrolyte system. The initial poor performance as rechargeable systems of the materials can be partially attributed the extremely low electrical and ionic conductivity of the electrode material, as demonstrated by electrochemical impedance spectroscopy (EIS) testing. Additionally, the surface microstructure was characterized using SEM and a localized secondary phase was found to develop unevenly on the surface during the first cycle of discharge that may also be inhibiting performance. The changes in thermodynamic properties were quantified using DSC/TGA for both energetic performance and battery safety at different states of charge. Due to the energetic nature of these materials, safety and an understanding of the reaction pathways and kinetics for both discharge and combustion is paramount.