Two thermoplastic triblock copolymers of poly(εcaprolactone)-based acidic (PCL-A) and basic (PCL-B) polymers are synthesized by atom transfer radical polymerization. PCL-A and PCL-B are sequentially electrospun on a sulfur electrode and then ionically cross-linked by an acid−base reaction via hot pressing at 70 °C, which is confirmed by infrared (IR) spectroscopy. The cross-linked PCL-A/PCL-B-electrospun sulfur electrode is assembled as a lithium−sulfur battery with an asymmetric gel polymer electrolyte. The cross-linked polymer is swollen by a liquid electrolyte to form an asymmetric gel polymer electrolyte. The cyclic voltammetry results indicate that the asymmetric gel polymer electrolyte can suppress the dissolution of lithium polysulfides (Li 2 S n ) into the electrolyte. Furthermore, the lithium−sulfur battery with the asymmetric gel polymer electrolyte exhibits enhanced cycle-life performance.