Compact Solid Electrolyte Interface Realization Employing Surface‐Modified Fillers for Long‐Lasting, High‐Performance All‐Solid‐State Li‐Metal Batteries

• Published in: Small (Weinheim an der Bergstrasse, Germany) Germany), 2024-11, Vol.20 (45), p.e2402001-n/a
• Main Authors: Jamal, Hasan, Khan, Firoz, Kim, Ji Hoon, Kim, Eunhui, Lee, Sang Uck, Kim, Jae Hyun
• Format: Article
• Language: English
• Subjects: composite solid‐state electrolytes; Decomposition; Electrolytes; Energy distribution; Energy of dissociation; Fillers; Free energy; Heat of formation; high ionic conductivities; inorganic fillers; Interface stability; Ion currents; Lewis acid; Lithium; Molecular dynamics; molecular dynamics simulations; Polyethylene oxide; Polymers; Solid electrolytes; surface modifications; Surface stability
• ISSN: 1613-6810; 1613-6829; 1613-6829
• DOI: 10.1002/smll.202402001

The implementation of polymer‐based Li‐metal batteries is hindered by their low coulombic efficiency and poor cycling stability attributed to continuous electrolyte decomposition. Enhancement of the solid electrolyte interface (SEI) stability is key to mitigating electrolyte decomposition. This study proposes surface‐functionalized silica mesoball fillers to fabricate a composite polymer electrolyte (MSBM‐CPE). As a result of surface modification, the polyethylene oxide matrix benefits from the uniform distribution of the filler, which provides a large surface area and Lewis acid sites. Molecular dynamics simulations reveal that the dissociation energy of lithium bis(trifluoromethanesulfonyl)imide in the filler is fourfold higher (−1.95 eV) than that of the filler‐free electrolyte. Consequently, the MSMB‐CPE diffusivity is 30 times higher than its filler‐free counterpart. The MSMB‐CPE of ionic conductivity of 1.16 × 10−2 S cm−1 @60 °C and a venerable Li‐ion transference number of 0.81. The excellent compatibility of MSMB‐CPE with the Li anode is demonstrated by its stable symmetric cell performance under high current density (200 µA cm−2 @60 °C) for over 5000 h. Approximately 85.60% retention capacity of the [Li/MSMB‐CPE/LiFePO4] full cell after 700 cycles. Furthermore, compositional analysis reveals that the SEI layer in MSMB‐CPE is smooth with fewer by‐products at the electrolyte/Li interface. This study presents a novel polymer electrolyte (MSBM‐CPE) with surface‐functionalized silica mesoball fillers, enhancing ionic conductivity and SEI stability. The electrolyte shows superior lithium‐ion transport and compatibility with the Li anode, achieving high conductivity, long cycling stability, and reduced dendrite formation. These findings highlight the potential of MSBM‐CPE for high‐performance Li‐metal batteries.