Thermal Conductive 2D Boron Nitride for High‐Performance All‐Solid‐State Lithium–Sulfur Batteries

Polymer‐based solid‐state electrolytes are shown to be highly promising for realizing low‐cost, high‐capacity, and safe Li batteries. One major challenge for polymer solid‐state batteries is the relatively high operating temperature (60–80 °C), which means operating such batteries will require significant ramp up time due to heating. On the other hand, as polymer electrolytes are poor thermal conductors, thermal variation across the polymer electrolyte can lead to nonuniformity in ionic conductivity. This can be highly detrimental to lithium deposition and may result in dendrite formation. Here, a polyethylene oxide‐based electrolyte with improved thermal responses is developed by incorporating 2D boron nitride (BN) nanoflakes. The results show that the BN additive also enhances ionic and mechanical properties of the electrolyte. More uniform Li stripping/deposition and reversible cathode reactions are achieved, which in turn enable all‐solid‐state lithium–sulfur cells with superior performances.