Descriptor‐Guided Dynamic Solvation‐Shell Reconstruction Enables PEO‐Based Polymer Electrolytes With 10.9 mS cm −1 Ionic Conductivity

ABSTRACT High‐voltage polymer electrolyte lithium metal batteries have long been constrained by the intrinsically low ionic conductivity of polymer electrolytes and unstable high‐voltage cathode interfaces, especially at low temperatures where ion transport and interfacial kinetics become sluggish. Here, we propose a descriptor‐guided dynamic solvation‐shell reconstruction strategy for poly(ethylene oxide) (PEO)‐based quasi‐solid electrolytes by introducing nitrile plasticizers with competitive Li + affinity and fast local Li + diffusivity. These nitrile ligands competitively enter the first Li + solvation shell, weaken persistent Li + ‐ether oxygen coordination, and shift Li + migration from polymer‐cage‐confined hopping to ligand‐exchange‐assisted transport. The optimized electrolyte achieves a room‐temperature ionic conductivity of 10.9 mS cm −1 , nearly three orders of magnitude higher than that of the pristine PEO electrolyte. Meanwhile, the nitrile‐containing solvation shell regulates interfacial decomposition pathways, suppresses oxidative PEO degradation in high‐voltage Li‖NCM811 cells, and promotes the formation of compact cathode electrolyte interphases. Benefiting from simultaneously enhanced bulk Li + transport and high‐voltage interfacial stability, the optimized electrolyte enables stable fast‐charging cycling and low‐temperature operation in Li‖NCM811 cells. This work establishes descriptor‐guided dynamic first‐solvation‐shell reconstruction as a molecular design principle for high‐conductivity, high‐voltage‐stable PEO‐based quasi‐solid electrolytes.