Sipra Mohapatra1,Santosh Mogurampelly1
Indian Institute of Technology Jodhpur1
Sipra Mohapatra1,Santosh Mogurampelly1
Indian Institute of Technology Jodhpur1
Biocompatible electrolytes are becoming attractive alternatives for the existing counterpart technology for battery electrolytes, as they are sustainable, renewable, and easily degradable. We used all-atom molecular dynamics simulations to study the transport and mechanical characteristics of a new class of battery electrolytes containing ethylene carbonate (EC), Li-TFSI, and pectin at different weight percentages. Pectin is a polysaccharide exhibiting high ion solvating capability, making it a potential candidate for battery electrolyte applications. Our simulation results demonstrate that pectin reduces the coordination numbers of lithium ions surrounding the counterions (and vice versa) as a result of the strong lithium-pectin interactions in comparison to lithium-TFSI interactions. We observed that smaller ionic clusters are favored over larger ones due to strong ion-polymer interactions, which is different from the trend observed in conventional electrolytes. Moreover, the ion association probability shows an increase in free ions, which indicates an enhancement in the overall ionic conductivity of pectin EC-LiTFSI electrolytes. Interestingly, TFSI ionic diffusivities show a strong correlation with the ion-pair relaxation timescales, with a relationship of <i>D<sub>TFSI</sub>∼ τ<sub>c</sub></i><sup>-0.95</sup>. On the other hand, the diffusivities of lithium ions follow a different pattern, with <i>D<sub>Li</sub>∼</i>τ<sub>c</sub><sup>-3.1</sup>, suggesting a unique transport mechanism for lithium ions. Consequently, the Nernst-Einstein conductivities scale with the ion-pair relaxation timescales as σ<sub>NE</sub>∼ τ<sub>c</sub><sup>1.85</sup>. Furthermore, the increase in viscosity and ion-pair relaxation timescales show that pectin can also enhance the mechanical stability of the electrolytes.<br/><br/>References:<br/>1. O. Borodin and G.D. Smith, <i>Macromolecules,</i> 2006, 39, 1620.<br/>2. S. Mohapatra et al.,<i> Nanoscale</i>, 2024, doi:10.1039/d3nr04029a<br/>3. S. Mogurampelly, J. R. Keith and V. Ganesan, <i>J. Am. Chem. Soc.</i>, 2017, 139, 9511–9514.<br/>4. Y. Zhang and E. J. Maginn, <i>J. Phys. Chem. Lett.</i>, 2015, 6, 700–705.