Enhanced Transformation Kinetics of Polysulfides Enabled by Synergistic Catalysis of Functional Graphitic Carbon Nitride for High‐Performance Li‐S Batteries

Abstract The introduction of an electrocatalyst to accelerate the kinetics of lithium polysulfides (LiPSs) reduction/oxidation is beneficial to enhance the capacity of sulfur cathode and inhibit the shuttling effect of LiPSs. However, current electrocatalysts mainly focus on the metal‐based active sites to reduce the reaction barriers, and there remains a great challenge in developing light‐weighted metal‐free catalysts. In this work, 1D graphitic carbon nitride nanorods (g‐C ₃ N ₄ ‐NRs) with carboxyl (─COOH) and acylamide (─CONH ₂ ) functional groups are designed as metal‐free electrocatalysts for lithium‐sulfur batteries to accelerate the transport of Li ⁺ and the conversion of LiPSs. The density functional theory (DFT) calculations prove that the existence of ─COOH group realizes the adsorption of LiPSs and accelerates the transport of Li ⁺ , while the ─CONH ₂ groups reduce the reaction energy barrier of S ₈ to Li ₂ S. In addition, in situ UV–vis and Li ₂ S nucleation/dissociation experiments also verify that g‐C ₃ N ₄ ‐NRs achieve rapid adsorption and transformation of LiPSs under the synergistic action of ─COOH and ─CONH ₂ functional groups. Consequently, the sulfur cathode based on the g‐C ₃ N ₄ ‐NRs‐PP separator remains at a specific capacity of 700.3 mAh g ⁻¹ after 70 cycles at 0.2 C, at 0 °C. This work provides a new strategy for breaking through the bottleneck of metal‐free catalysts for high‐performance lithium‐sulfur batteries.