Research Projects

Sodium ion batteries (SIBs) are attractive due to the abundance of sodium on earth’s crest. In fact, the deposits are spread across the globe, hence there are no geopolitical issues. The energy density of SIBs is lower than that of Li ion batteries. Energy density of a battery is a combination of cell voltage and quantity of charges stored. Thus, one can increase the energy density by increasing the cell voltage of the battery. The bottle neck in increasing the cell voltage is the electrolyte that are not stable at high voltages. The solvation sphere is an important component in the formation of electrode electrolyte interface. The molecules and ions in the solvation sphere decompose to form electrode electrolyte interface that is popularly known as solid electrolyte interface (SEI). Many approaches have been developed to manipulate the solvation sphere and form a stable SEI. For example, a carbonate with vinylene functionality has been added as an additive. The vinylene moiety polymerizes and stabilizes the SEI. Ionic liquids, fluoro compounds, sulfones and nitriles have also been used as additives. High concentration electrolytes facilitate anion derived SEI. Recently, Nylon 6 is explored in high voltage sodium ion batteries. Interestingly, Nylon 6, is soluble in ethylene carbonate and dimethyl carbonate solvent mixture. The SIB’s with electrolyte comprising NaPF6 and Nylon 6 showed stable performance in the potential window of 0.01 - 4.4 V vs Na/Na+. The electron density of amide functionality and its distribution along the polymer backbone plays an important role in restructuring the solvation sphere. The coiled structure of Nylon has also been attributed to the restructuring of solvation sphere. However, it is well known that the electron distribution is poor in alkyl chains compared to aromatic units. This is one of the origins of the proposal. To facilitate electron distribution, molecules with aromatic units will be prepared, including graphene dots. The proposed molecules will have multiple amide moieties and aromatic units to modulate the electron density distribution. The coiled structure of a linear polymer can’t be controlled. If indeed the coiled structure played a role, we need to identify the effect of coiling on solvation sphere formation. Dendrimers are polymers with well-defined structure, hence they are probably most suited to understand this phenomenon. Thus, we propose to synthesize a few amide based dendrimers of various generations and study their role in the operation of high voltage SIBs. Are polyamides the only choice? The answer is probably NO. Urethanes and ureas are close analogs of amides, hence they need to be explored in the fabrication of high voltage SIBs. From our own work, we do know the suitability of urethane and urea moieties’ in rechargeable battery electrodes. Therefore, we propose to study the effect of polyurethane in restructuring the solvation sheath of sodium ions. We propose to synthesize urethane containing small molecules and dendrimers. We will also synthesize urea containing small molecules and dendrimers. We will synthesize urea and urethane containing conjugated molecules that would form a conducting polymer films on SEI. The solvation energy must be studied by density functional theory, which will be carried out by my collaborator Dr Sailaja Krishnamurty. The Graphenes will be synthesized and characterized by Dr Parameshwari, who is an expert on carbon material synthesis and Raman Spectroscopy. This is a fundamental study, but has a potential in SIBs manufacturing. Therefore, I shared the proposal with Reliance Industries and they have provided letter of intent, which is attached with the proposal.