Effect of mechanical strain on lithium-ion transport between cellulose nanostrands and polyethylene oxide

Cellulose nanofibril-reinforced polyethylene oxide glycol (PEO) has attracted attention as a next-generation electrolyte material because of its excellent stability and flexibility. To maximize these advantages, ion conductivity in the mechanically deformed state is necessary. To help achieve this, molecular dynamics simulations were used to investigate the Li⁺ transport kinetics inside the PEO/cellulose nanostrand (CNS). The crown-binding structure of PEO for Li⁺ is broken by the uniaxial tensile deformation of the electrolyte; therefore, the hopping dynamics of the ions are promoted in PEO. However, the ion conductivity of the PEO/CNS instead decreased significantly under mechanical stretching. This was due to the loss of the Coulombic driving force passed by the hydroxy groups on the CNS. In other words, electrolyte deformation may deteriorate the electrochemical properties of flexible electrolytes and should be considered when designing anisotropic nanocomposites. Our results call for further exploration of strategies for reinforcing the interfacial ion transport kinetics in practical CNS-reinforced electrolyte designs.