Enabling Long-Cycle Li–S Batteries at −20 °C via Activation of Li ₂ S Redox Kinetics with Co and Mo ₂ C Nanospheres

As a potential high-safety and high-energy-density technology, lithium sulfide has been extensively studied as a cathode material for lithium-sulfur batteries under room temperature conditions. However, limited by its intrinsic characteristics of low electronic conductivity and high activation energy barrier, conventional Li₂S cathodes struggle to overcome the activation energy barrier at low temperatures, resulting in scarce research on their application below zero. Specifically, studies on operation at -20 °C are nearly nonexistent. Herein, a synergistic strategy combining molybdenum carbide support adsorption and cobalt metal catalysis is proposed for low-temperature performance investigation. Via a lithiation reaction, Li₂S@MoC-Co nanocomposites are fabricated by in situ synthesizing Li₂S nanoparticles, introducing MoC as the support, and incorporating Co metal. When assembled into batteries with Li₂S@MoC-Co as the cathode and metallic lithium as the anode, the activation energy barrier is reduced to 2.41 V at room temperature, exhibiting excellent electrochemical performance. A high initial discharge capacity of 1100 mAh g⁻¹ is achieved at 0.1 C, and a discharge capacity of 430 mAh g⁻¹ is retained after 200 cycles at 0.5 C. Even at -20 °C, Li₂S is almost fully activated during the first charging cycle, delivering a discharge capacity of 360 mAh g⁻¹ at 0.05 C. Moreover, a capacity retention rate of 92% is maintained after 300 cycles at 0.5 C. This work realizes high output and high-capacity retention of Li₂S at -20 °C, providing a new paradigm for the development of low-temperature Li₂S-based batteries.