Ta-doped　Li7La3Zr2O12　(LLZTO)　solid-state　electrolytes　(SEs)　show　great　promise　for　solid-state　batteries　due　to　its　high　conductivity　and　safety.　However,　one　of　the　challenges　it　faces　is　lithium　dendrite　propagation　upon　long-term　cycling.　To　address　this　issue,　we　propose　the　incorporation　of　fumed　silica　(FS)　at　the　grain　boundaries　of　LLZTO　to　modify　the　properties　of　the　garnet　pellet,　which　effectively　inhibits　the　dendrite　growth.　The　introduction　of　FS　has　demonstrated　several　beneficial　effects.　Firstly,　it　reduces　the　migration　barrier　of　lithium　ions,　which　helps　prevent　dendrite　formation　and　propagation.　Additionally,　FS　reduces　the　electronic　conductivity　of　the　SEs　pellet,　suppressing　the　dendrite　formation.　Moreover,　the　formed　lithium　silicates　from　FS　might　also　be　acted　as　electron　inhibitor,　thus　inhibiting　the　lithium　dendrite　growth　upon　cycling.　By　investigating　the　use　of　FS　as　a　modifier　in　LLZTO-based　electrolytes,　our　study　contributes　to　advancing　dendrite-free　solid-state　electrolytes　and　thus　the　development　of　high-performance　all-solid-state　batteries.　©　2024　Wiley-VCH　GmbH.