context: In summary, we have demonstrated a flexible organic–inorganic composite solid electrolyte consisting of polymer PEO, Li salt (LiTFSI), ionic liquid (BMP-TFSI), and the ceramic ion conducting LATP particles. The addition of BMP-TFSI can not only decrease the interface impedance between the polymer matrix and LATP particles, but also enhance the stability of the composite electrolyte and Li metal anode. Benefitting from the synergistic effect of the organic–inorganic complex, the PBL-CSE membrane shows improved electrochemical properties. The ionic conductivity is above 10−4 S cm−1 at 30 °C. The electrochemical stability window is up to 5.0V (vs. Li+/Li) and the Li+ transference number is 0.48. The PBL-CSE exhibits superb interface stability and impressive capacity against a Li electrode, as well as effective suppression of Li dendrite growth. The assembled solid-state LiFePO4/Li batteries demonstrated excellent cycling stability with a high specific capacity and very large capacity retention at 0.5C at 45 °C, as well as 0.3C at 30 °C. Furthermore, LiFePO4/PBL-CSE/Li all-solid-state pouch cells also demonstrate high flexibility and safety. Thus, this work represents a promising composite electrolyte for high performance, safe and high energy density all-solid-state lithium metal batteries.
answer: Li metal