High temperature lithium-sulfur batteries are seldom investigated due in part to the lack of mechanical robust separators and the more serious parasitic polysulfide shuttle effects at elevated temperature. Here, we for the first time present high performance lithium-sulfur cells that can be cycled at elevated temperature of 100 °C via designing asymmetric functionalized polyimide-based separators using a facile and scalable blade-casting method. In this sandwich configuration, polyimide nonwovens act as electrochemically and mechanically robust skeleton while Super-P nanoparticles coating and poly (ethylene oxide)-integrated-lithium lanthanum zirconium oxide coating render additional functions of immobilizing polysulfides and inhibiting lithium dendrite growth, respectively. By virtue of the multifarious functions of the modified polyimide-based separator, a high specific capacity of 1474.3 mAh g−1 without severe over-charge behavior is also firstly demonstrated at a higher temperature of 100 °C. Additionally, Li-S cells using the modified polyimide -based separator deliver excellent cycling stability (only 0.2% capacity decay cycle−1 on average exceeding 200 cycles at 80 °C) at a relatively high rate of 5C. The experimental results validate the pivotal role of newly designed separators for high performance lithium-sulfur chemistry especially at elevated temperature.