Ionic liquid derived Li6.4La3Zr1.4Ta0.6O12/polyethylene oxide solid electrolyte for high stable lithium metal batteries

Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (LLZTO) is widely used in polyethylene oxide (PEO) based solid electrolytes preparation due to its high ionic conductivity, electrochemical stability towards lithium and excellent mechanical properties. However, agglomeration of LLZTO and the inert interfacial layer for Li⁺ transport between LLZTO and PEO limit its application. Herein, we systematically study the effect of different contents of 1-methyl-1-propylpiperidinium bis(trifluoromethylsulfonyl)imide (denoted as PP13-TFSI) ionic liquid on PEO/LLZTO composite solid electrolytes (CSEs). PP13-TFSI, which provides a new pathway for Li⁺ transport and promotes the uniform dispersion of LLZTO. By adjusting the proportion of PP13-TFSI reasonably, the agglomeration of LLZTO is weakened, the crystallinity of PEO is reduced, and the growth of lithium dendrites is also inhibited. Therefore, the CSEs with high ionic conductivity (2.03 × 10⁻⁴ S cm⁻¹, 30 ℃) enhanced by PP13-TFSI. Li||Li symmetric batteries exhibit stable cycling up to 6000 h at 60 °C, and can cycle stably for up to 3000 h at 28 °C. LiFePO₄||Li full batteries exhibit high-capacity retention rate (≈ 90.5 %) after 500 cycles at 1 C. This work not only systematically study the effects of different contents of PP13-TFSI on CSEs, but also provide a simple composite solid electrolyte strategy.