biostudies-literatureUnknown21(37)Kuo TYNational Science and Technology Council (NSTC), TaiwanSolid-state lithium batteries (SSLBs) with composite solid electrolytes (CSEs) offer enhanced energy density and high safety. However, their performance is hindered by large thickness and limited Li⁺ conductivity of CSEs, and large electrode/electrolyte interface resistance. This study develops an 18 µm-thick CSE using a polyethylene scaffold, which incorporates garnet-type Li_6.25La₃Zr₂Ga_0.25O₁₂ (LLZGO) oxide and an ionic liquid (IL) additive in a poly(vinylidene fluoride-co-hexafluoropropylene)/polypropylene carbonate matrix, achieving a high ionic conductivity of 8.6 × 10^-4 S cm^-1 at 30 °C. The IL increases Li⁺ conduction of the CSE and reduces the interfacial resistance. The constructed LiNi<sub>0.8<Small (Weinheim an der Bergstrasse, Germany)e03865https://www.ebi.ac.uk/biostudies/studies/S-EPMC12444873biostudies-literatureIonic Liquid Enabled High-Energy-Density Solid-State Lithium Batteries with High-Areal-Capacity Cathode and Scaffold-Supported Composite Electrolyte.PMC12444873Dhaka RSYang CCChung TFLi JChang JKHsiao CNChen CCPatra JHsieh CTTseng CJKuo TYfalseIonic Liquid Enabled High-Energy-Density Solid-State Lithium Batteries with High-Areal-Capacity Cathode and Scaffold-Supported Composite Electrolyte.Solid-state lithium batteries (SSLBs) with composite solid electrolytes (CSEs) offer enhanced energy density and high safety. However, their performance is hindered by large thickness and limited Li⁺ conductivity of CSEs, and large electrode/electrolyte interface resistance. This study develops an 18 µm-thick CSE using a polyethylene scaffold, which incorporates garnet-type Li_6.25La₃Zr₂Ga_0.25O₁₂ (LLZGO) oxide and an ionic liquid (IL) additive in a poly(vinylidene fluoride-co-hexafluoropropylene)/polypropylene carbonate matrix, achieving a high ionic conductivity of 8.6 × 10^-4 S cm^-1 at 30 °C. The IL increases Li⁺ conduction of the CSE and reduces the interfacial resistance. The constructed LiNi<sub>0.8<2025-01-01T00:00:00Z2025 Sep2026-06-03T14:37:24.152Z2026-05-29T03:05:16.706ZS-EPMC124448734071482010.1002/smll.202503865