In-Situ Polymerized\nHigh-Voltage Solid-State Lithium Metal Batteries with Dual-Reinforced\nStable Interfaces

Solid polymer electrolytes (SPEs) represent a pivotal\nadvance toward\nhigh-energy solid-state lithium metal batteries. However, inadequate\ninterfacial contact remains a significant bottleneck, impeding scalability\nand application. Inadequate interfacial contact remains a significant\nbottleneck, impeding scalability and application. Recent efforts have\nfocused on transforming liquid/solid interfaces into solid/solid ones\nthrough in situ polymerization, which shows potential especially in\nreducing interface impedance. Here, we designed high-voltage SSLMBs\nwith dual-reinforced stable interfaces by combining interface modification\nwith an in situ polymerization technology inspired by targeted effects\nin medicine. Theoretical calculations and time-of-flight secondary\nion mass spectrometry (TOF-SIMS) analysis demonstrate that tetramethylene\nsulfone (TMS) and bis(2,2,2-trifluoromethyl) carbonate (TFEC) exhibit\nselective adsorption at the interface of the LiNi<sub>0.8</sub>Co<sub>0.1</sub>Mn<sub>0.1</sub>O<sub>2</sub> (NCM) cathode and Li anode,\nrespectively. These compounds further decompose to form a stable cathode–electrolyte\ninterface (CEI) film and a solid electrolyte interface (SEI) film,\nthereby simultaneously achieving a superior interface between the\nSPE and both the Li anode and NCM cathode. The developed Li||SPE||Li\ncell sustained cycling for more than 1000 h at 0.3 mA cm<sup>–2</sup>, and the NCM||SPE||Li cell also demonstrated an excellent capacity\nretention of 86.8% after 1000 cycles at 1 °C. This work will\nprovide valuable insights for the rational design of high-voltage\nSSLMBs with stable interfaces, leveraging in situ polymerization as\na cornerstone technology.