Decoupling Surface Rigidity from Bulk Compliance in Elastomeric Electrolytes via Surface-Architected MXene Interphase Engineering

Elastomeric electrolytes provide intimate interfacial contact but lack sufficient mechanical strength to suppress lithium dendrites. We address this trade-off via surface-architected MXene interphase engineering on a hydrogenated nitrile butadiene rubber (HNBR) matrix. The high-modulus (1.5 GPa) surface layer mechanically suppresses dendrite protuberance via stress redistribution, while the compliant bulk preserves conformal contact. Concurrently, a lithiophilic, oriented MXene network promotes uniform ion flux, affording an ionic conductivity of 8.05 × 10 –4 S cm –1 and enhanced Li + transport relative to the pristine matrix. This mechano-ionic coupling enables dendrite-free cycling exceeding 7000 h and stable full-cell operation with high-loading LiFePO 4 (1.81 mAh cm –2 ) and high-voltage NCM622 (4.3 V). This interphase engineering strategy establishes surface-bulk mechanical decoupling as a generalizable design principle for developing high-energy-density, flexible lithium–metal batteries.