Self‐Assembled Ionic Clusters Accelerate Li‐Ion Transport Through Microphase‐Separated Polyelectrolytes

ABSTRACT Precise, molecular‐level control of ion coordination and mesoscale morphology is essential for pushing solid polymer electrolytes toward the conductivity and mechanical robustness metrics demanded by next‐generation batteries. Here we introduce an elastic microphase polyelectrolyte (EMP) whose thermodynamically driven microphase separation self‐assembles Li + ‐rich ionic clusters. These clusters stitch together a dynamic, percolating conduction network that achieves high ionic conductivity of 2.9 × 10 −4 S cm −1 and a high Li + transference number of 0.67 at room temperature. Operando galvanostatic impedance spectroscopy uncovers a field‐responsive boost in conductivity—from 4.1 × 10 −4 to 1.9 × 10 −3 S cm −1 as the current density increases from 25 to 200 µA cm −2 —evidence of bias‐induced cluster reconfiguration. Mechanically, the EMP combines high elasticity with self‐healing, ensuring intimate, long‐lived electrode contact. When paired with a LiNi 0.8 Co 0.1 Mn 0.1 O 2 cathode, solid‐state cells retain 93.92% of their initial capacity after 50 cycles under a high‐capacity loading of ∼2.0 mAh cm −2 . By demonstrating how supramolecular ionic assembly can be harnessed to couple ion transport, mechanics, and electrochemical stability, this work lays a versatile design platform for high‐performance, solid‐state lithium batteries.