Dielectric‐Tailored Space Charge Layer and Ion Coordination Structure for High‐Voltage Polymer All‐Solid‐State Lithium Batteries

Abstract The poor structural stability of polymer electrolytes and sluggish ion transport kinetics of interfaces with cathode limit the fundamental performance improvements of polymer all‐solid‐state lithium metal batteries under high voltages. Herein, it is revealed that by introducing dielectric BaTiO₃ in an in‐situ polymerized composite solid‐state electrolyte, the generated interaction between the ether group of polymer electrolyte and dielectric material could effectively regulate the lithium‐ion (Li⁺) coordination structure to achieve an oxidative potential higher than 5.2 V. The dielectric BaTiO₃ with spontaneous polarization also weakens the space charge layer effect between the cathode and electrolyte, facilitating fast Li⁺ transport kinetics across the cathode/electrolyte interfaces. The all‐solid‐state LiNi_0.8Co_0.1Mn_0.1O₂/Li batteries with the dielectric composite solid‐state electrolyte exhibit an ultra‐long cycling life of 1800 and 1300 cycles at room temperature under high cut‐off voltages of 4.6 and 4.7 V, respectively. This work highlights the critical role of dielectric materials in high‐performance solid‐state electrolytes and provides a promising strategy to realize high‐voltage long‐life all‐solid‐state lithium metal batteries.