Organosulfur materials containing sulfur–sulfur bonds are an emerging class of high-capacity cathodes for lithium storage. However, it remains a great challenge to achieve rapid conversion reaction kinetics at practical testing conditions of high cathode mass loading and low electrolyte utilization. In this study, a Li-rich pyrolyzed polyacrylonitrile/selenium disulfide (pPAN/Se₂S₃) composite cathode is synthesized by deep lithiation to address the above challenges. The Li-rich molecular structure significantly boosts the lithium storage kinetics by accelerating lithium diffusivity and improving electronic conductivity. Even under practical test conditions requiring a lean electrolyte (Electrolyte/sulfur ratio of 4.1 μL mg⁻¹) and high loading (7 mg cm⁻² of pPAN/Se₂S₃), DL-pPAN/Se₂S₃ exhibits a specific capacity of 558 mAh g⁻¹, maintaining 484 mAh g⁻¹ at the 100th cycle with an average Coulombic efficiency of near 100%. Moreover, it provides (electro)chemically stable Li resources to offset Li consumption over charge–discharge cycles. As a result the as-fabricated anode-free cell shows a superior cycling stability with 90% retention of the initial capacity over 45 cycles. This study provides a novel approach for fabricating high-energy and stable Li–SPAN cells.