Nanoporous Polymer Films with a High Cation Transference Number Stabilize Lithium Metal Anodes in Light-Weight Batteries for Electrified Transportation

To suppress dendrite formation in lithium metal batteries, high cation transference number electrolytes that reduce electrode polarization are highly desirable, but rarely available using conventional liquid electrolytes. Here, we show that liquid electrolytes increase their cation transference numbers (e.g., ∼0.2 to >0.70) when confined to a structurally rigid polymer host whose pores are on a similar length scale (0.5–2 nm) as the Debye screening length in the electrolyte, which results in a diffuse electrolyte double layer at the polymer–electrolyte interface that retains counterions and reject co-ions from the electrolyte due to their larger size. Lithium anodes coated with ∼1 μm thick overlayers of the polymer host exhibit both a low area-specific resistance and clear dendrite-suppressing character, as evident from their performance in Li–Li and Li–Cu cells as well as in post-mortem analysis of the anode’s morphology after cycling. High areal capacity Li–S cells (4.9 mg cm–2; 8.2 mAh cm–2) implementi...