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

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_0.8Co_0.1Mn_0.1O₂ 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.