PEO/LLZTO Composite Electrolytes for Li-S Batteries

Lithium-sulfur batteries (LSBs) have the advantages of high specific capacity and high energy density, which attracted attention in the past decade. However, poor safety and polysulfide shuttle phenomenon are the two most criticized reasons for liquid LSBs. Using solid-state electrolytes can overcome those problems, but compared with liquid electrolytes, solid electrolytes have lower ionic conductivity and poorer electrode/electrolyte interface contact in all-solid-state LSBs. Herein, we combined polymer polyethylene oxides (PEO), Li-ion conducting ceramic powder, Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (LLZTO), dispersant, and plasticizer to form PEO/LLZTO composite electrolyte. The ionic conductivity of PEO/LLZTO composite electrolyte is approximately 10⁻⁴ S cm⁻¹ at room temperature. Furthermore, the capacity of the all-solid-state LSB assembled with the sulfur cathode, Li metal anode, and PEO/LLZTO composite electrolyte can reach up to >1000 mAh g⁻¹. After 100 cycles at a current density of 0.2C at room temperature, the S//PEO/LLZTO//Li batteries still exhibited high capacity retention of up to 70%, showing high potential for all-solid-state LSB applications.