Lithium-sulfur (Li–S) batteries have attracted significant interest owing to their elevated energy densities. However, achieving sufficient sulfur loading for the cathode in Li–S batteries remains a challenging task for the practical application of Li–S batteries. In this study, activated carbon (AC) was synthesized from palm kernel shells using three distinct activation methods to develop well-defined porosity as a sulfur host. Among these methods, the double-step activation demonstrated the most remarkable sulfur uptake of 81.74% by weight. This exceptional adsorption performance is attributed to the synergistic effects of KOH activation and double physical activation, which together result in the formation of well-developed pores in the AC. The substantial sulfur encapsulation achieved in this study significantly improves the specific discharge capacity of Li–S batteries.