Polymer Side‐Chain Electronic Effects Regulating Solvation Sheath for Low‐Temperature and High‐Voltage Lithium Metal Batteries

ABSTRACT

Gel polymer electrolytes (GPEs) rich in ether oxygen side chains have attracted particular interests in high‑energy‑density lithium metal batteries (LMBs). However, the strong coordination between their polymer framework and lithium ions (Li ⁺ ) leads to a high desolvation energy barrier at low temperatures. Herein, by comparing the side‑chain electronic effects, this work constructs an ether‐oxygen‐based gel polymer electrolyte (E‐GPE) with electron‐donating ether oxygen side chains and a fluorinated GPE (F‐GPE) with electron‐withdrawing trifluoromethyl side chains, with N,N‐dimethyl trifluoroacetamide (FDMA) as a low‐temperature additive. Density functional theory (DFT) calculations reveal that the electron‐donating side chains in E‐GPE enhance the binding energy between the polymer framework and Li ⁺ , thereby impeding Li ⁺ desolvation. Conversely, the electron‐withdrawing side chains in F‐GPE weaken the binding energy between the polymer framework and Li ⁺ , lowering the Li ⁺ desolvation barrier and inducing the formation of LiF‐rich interphase. Consequently, Li/F‐GPE/Li cells stably cycle for over 1000 h at −20°C, and Li/F‐GPE/LiCoO ₂ coin cells retain 88.7% of their original capacity after 400 cycles at −20°C. Furthermore, pouch cells steadily power a light‐emitting diode (LED) after shear damage, demonstrating potential safety. This work provides a new design paradigm for developing GPEs for high‐energy‐density LMBs in extreme environments.