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 Li 2 S 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, Li 2 S@MoC–Co nanocomposites are fabricated by in situ synthesizing Li 2 S nanoparticles, introducing MoC as the support, and incorporating Co metal. When assembled into batteries with Li 2 S@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, Li 2 S 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 Li 2 S at −20 °C, providing a new paradigm for the development of low-temperature Li 2 S-based batteries.