Facilitating uniform lithium-ion transport via polymer-assisted formation of unique interfaces to achieve a stable 4.7 V Li metal battery.

Achieving stable cycling of lithium metal batteries (LMBs) at high voltages presents a significant challenge due to interfacial instability and uneven lithium-ion transport, leading to dendrite formation and cathode degradation. Constructing a solid-electrolyte interphase (SEI) that facilitates fast and uniform ion transport is crucial for enhancing the stability of electrode structures. However, current research mainly focuses on interfacial instability while neglecting uneven ion transport, which is even more critical. In this study, we develop a novel electrolyte system, PAFE, by incorporating aluminum ethoxide (Al(EtO)₃), fluoroethylene carbonate (FEC), and pentafluorocyclotriphosphazene (PFPN) into a carbonate-based electrolyte. Al(EtO)₃ serves as a crosslinking agent, facilitating the formation of a three-dimensional polymer network that promotes the uniform deposition of inorganic components such as LiF, Li₃N, Li₃P and Al₂O₃ within the SEI and cathode-electrolyte interphase (CEI). These uniform interphases lower the activation energy for lithium-ion transport, thereby ensuring consistent ion flow and reducing internal stress within the electrodes. As a result, Li||LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) cells with PAFE exhibit exceptional cycling stability, retaining 80% capacity over 140 cycles at a high cut-off voltage of 4.7 V. Furthermore, 1 Ah pouch cells demonstrate excellent cycling performance, highlighting the potential of this electrolyte system for practical high-energy-density LMB applications.