  We investigate the effect of pectin on the structure and ion transport
properties of the room-temperature ionic liquid electrolyte
1-n-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) using molecular
dynamics simulations. We find that pectin induces intriguing structural changes
in the electrolyte that disrupt large ionic aggregates and promote the
formation of smaller ionic clusters, which is a promising finding for ionic
conductivity. Due to pectin in [BMIM][PF6] electrolytes, the diffusion
coefficient of cations and anions is observed to decrease by a factor of four
for a loading of 25 wt. % of pectin in [BMIM][PF6] electrolyte. A strong
correlation between the ionic diffusivities (D) and ion-pair relaxation
timescales ($\tau_C$) is observed such that D~$\tau_C^{-0.75}$ for cations and
D~$\tau_C^{-0.82}$ for anions. The relaxation timescale exponents indicate that
the ion transport mechanisms in pectin-[BMIM][PF6] electrolytes are slightly
distinct from those found in neat [BMIM][PF6] electrolytes (D~$\tau_C^{-1}$).
Since pectin marginally affects ionic diffusivities at the gain of smaller
ionic aggregates and viscosity, our results suggest that pectin-IL electrolytes
offer improved properties for battery applications, including ionic
conductivity, mechanical stability, and biodegradability.
