Reinforcing interfacial compatibility of LLZTO/PVDF-HFP composite electrolytes by chemical interaction for solid-state lithium metal batteries

Composite electrolytes (CEs) have a significant potential for achieving excellent safety and energy density in solid-state lithium metal batteries owing to applicable ionic conductivity, easy fabrication, and good electrochemical properties. However, achieving good interfacial compatibility between inorganic fillers and polymer matrix remains challenging. Herein, we design a Li6.4La3Zr1.4Ta0.6O12 filler modified with isopropyl tri(dioctyl pyrophosphate) titanate for poly (vinylidene fluoride-co-hexafluoropropylene) electrolyte (denoted as Ti@LLZTO/PVDF-HFP). We reveal the enhanced mechanism of a modified interface on the electrochemical performance by combining experimental results and theoretical calculations. The reinforced interface can facilitate the uniform dispersion of filler in the polymer matrix as well as dissociate more lithium salt, which enables enhanced ionic conductivity (6.86 x 10-5 S cm-1 at 30 degrees C). Besides, the Ti@LLZTO can immobilize the anions in lithium salt via hydrogen bonding interactions and the Ti-O chemical bonding. Consequently, the Li|| Ti@LLZTO/PVDF-HFP||Li cell shows great cyclability over 1550 h at 0.1 mA cm-2, 0.1 mAh cm-2. Moreover, the Li||Ti@LLZTO/PVDF-HFP||LFP cell achieves superior cycling stability at 0.5 C with a high Coulombic efficiency of 98.8 %. This work provides an insightful understanding of designing good interfacial compatibility for advanced composite electrolytes.