New polymer coating dramatically speeds lithium flow in solid-state batteries
Researchers discovered that swapping one polymer for another can increase ion transfer speeds 32-fold at the interface where lithium moves through solid-state batteries. The finding offers a concrete design lever for manufacturers seeking to improve battery performance without overhauling existing materials—potentially shortening development timelines for next-generation electric vehicles and grid storage.
Originaltitel: Li-Ion Transfer at the LLZO–Polycaprolactone Interface: Role of Polymer Chemistry in Interfacial Transport
Hybrid polymer–ceramic electrolytes are promising candidates for solid-state lithium batteries, yet ion transport across polymerceramic interfaces often limits performance. Here, atomistic molecular-dynamics simulations are used to investigate Li-ion exchange at the Li7La3Zr2O12 (LLZO)–poly(ε-caprolactone) (PCL) interface and to compare directly with LLZO–poly(ethylene oxide) (PEO) at comparable lithium loading. The LLZO–PCL interface exhibits pronounced interfacial structuring, including strong adsorption of carbonyl oxygen atoms at the ceramic surface and a well-defined first Li+ layer. Li-ion transfer across the interface is quantified from transition statistics and analyzed using free-energy profiles along the surface-normal coordinate. At 700 K, LLZO–PCL shows a substantially higher exchange rate than LLZO—PEO (factor 32), primarily due to a significantly lower free-energy barrier for polymer–ceramic transfer, consistent with weaker Li+ coordination in PCL. An overdamped Kramers analysis together with the intra-well autocorrelation function confirms strongly damped local dynamics and suggests differences in effective friction between the minimum and the barrier region. Overall, the results demonstrate that polymer chemistry controls interfacial Li-ion transfer mainly via the barrier height, identifying polymer coordination strength as a key design parameter for reducing interfacial resistance in hybrid solid electrolytes.