The need for creating safe electrolytes for lithium batteries is significant given the continued safety problems associated with current lithium-ion batteries. Nonflammable polymer electrolytes offer a possible solution. In this talk, I will discuss some of the fundamental factors that limit ion transport in polymers. A crucial parameter of any electrolyte is the limiting current, the current at which the negative electrode is depleted of lithium ions due to concentration polarization. We show that nanostructured block copolymer electrolytes with a lamellar morphology undergo significant morphological changes as they accommodate large currents. Near the negative electrode, lamellae aligned perpendicular to the path of ion transport shrink preferentially as they depleted of salt, relative to lamellae aligned in the parallel direction near the negative electrode. The parallel lamellae provide avenues for ion transport and this could be deduced by intuition. The perpendicular lamellae play a surprisingly important role. They accommodate salt concentration gradients necessary for battery operation, and this is not readily deduced by intuition. Consequently, the limiting current in block copolymers is dictated by the extent to which lamellae can swell, rather than local salt concentration.

Response of nanostructured block copolymer electrolytes to large currents in lithium batteries

ACS Spring 2022

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