Valence-Adaptable Ni/Co Catalysis for High-Rate Sodium-Sulfur Batteries with Wide-Temperature Operation from -20 to 50 °C.

Abstract

To address the challenges posed by diverse global climates, the development of wide-temperature-operable batteries is essential. Here Ti₃C₂O_x is used as inner sheets to support the growth of NiCo-LDH wrinkles, forming a unique cavity-structured sulfur host. The resulting cathode demonstrates state-of-the-art high-rate performance, delivering a remarkable capacity of 1130.7 mAh g^-1 at 5 A g^-1 over 1200 cycles. It also exhibits outstanding wide-temperature operation, maintaining capacities of 1150.0 mAh g^-1 at 50 °C (5 A g^-1) and 969.1 mAh g^-1 at -20 °C (1 A g^-1) after 600 cycles. This exceptional performance across temperatures is attributed to the reversible redox behavior of the Ni^2.32+ ↔ Ni^2.54+ and Co^2.46+ ↔ Co^2.84+ redox couples. These transition metals from NiCo-LDH act as electron donors during discharge (from S₈ to Na₂S) and as electron acceptors during charge (from Na₂S to S₈), thereby accelerating electron transfer and enabling efficient polysulfide conversion even at low temperatures. Furthermore, adsorption experiments and density functional theory (DFT) calculations reveal that NiCo-LDH preferentially adsorbs short-chain polysulfides (Na₂S/Na₂S₂), while Ti₃C₂O_x exhibits stronger affinity for long-chain polysulfides (Na₂S₄/Na₂S₆). This synergistic adsorption behavior enhances polysulfide retention and mitigates the shuttle effect, contributing to excellent performance stability even at high temperatures.