Unlocking the Polarization and Reversibility Limitations for Stable Low‐Temperature Lithium Metal Anodes

The subzero‐temperature service of lithium (Li) metal anode has been enormously restricted by a large working polarization and a poor reversibility. In this contribution, the overpotential attributions during low‐temperature Li electroplating are deconvolved, and the interplay among the dominating kinetic overpotential, the dynamic solid electrolyte interphase (SEI) chemistry, and the corresponding cycling reversibility of Li metal is established. Specifically, by employing a localized highly concentrated electrolyte as a model system, it is disclosed that ionic concentration gradient plays a predominate role in polarizing the cathodic Li electroplating process at subzero working temperature. Inspired by this, a decoupling electrolyte design strategy is presented to synchronously tame the kinetic polarization and build a dynamically stable anion‐derived SEI, thus boosting a remarkably enhanced Coulombic efficiency of Li with a depressed cell overpotential and a more than three times longer lifespan in practical Li | LiNi 0.5 Co 0.2 Mn 0.3 O 2 cells at −20 °C. Herein, the essence to affecting the polarization and reversibility of low‐temperature working Li metal anode is uncovered, affording critical design principles to facilitate a stable dynamic interface for the high‐efficiency cycling of practical Li metal batteries at subzero temperatures.