Superior sulfur conversion reaction on phosphorus-doped carbon dot/graphene composites for Li–S batteries in a wide working temperature range

Achieving operational temperature resilience is a paramount design criterion for energy storage systems deployed under extreme environmental conditions. Lithium-sulfur batteries confront dual challenges of thermally exacerbated polysulfide shuttle effects at elevated temperatures and sluggish reaction kinetics under cryogenic conditions. To overcome these limitations, we developed a biomass-derived methodology that enabled simultaneous in-situ phosphorus doping of carbon quantum dots and their covalent immobilization on graphene substrates. The resulting phosphorus-doped carbon quantum dots/graphene (PCD-Gr) nanocomposite achieved exceptional doping concentrations in carbon nanomaterials. This multifunctional electrocatalyst as a sulfur host architecture can facilitate rapid adsorption-transfer-catalytic dynamics through truncated lithium-ion diffusion pathways and targeted acceleration of rate-limiting electrochemical processes. The synergistic mechanism effectively suppressesed polysulfide migration at high thermal loads while enhancing sulfur redox efficiency in subzero environments. Consequently, cells incorporating porous PCD-Gr matrices demonstrated remarkable rate performance and cycling stability across an expansive temperature range (−30–65 ℃). This dual-temperature optimization strategy established a blueprint for developing next-generation lithium-sulfur batteries with full-climate operational capabilities.