Modality-Tunable\nExfoliated N‑Doped Graphene\nas Effective Electrolyte Additive for High-Performance Lithium–Sulfur\nBatteries

While chemically doped graphene has\nshown great promise, the lack\nof cost-effective manufacturing has hindered its use. This study utilizes\na facile fabrication approach for modality-tunable N-doped graphene\nvia thermal annealing of aqueous-phase-exfoliated few-layered graphene\nfrom a Taylor–Couette reactor. This method demonstrates a high\nlevel of N-doping (27 atom % N) and offers modality tunability of\nthe C–N bond without foregoing scalability and green chemistry\nprinciples. The resulting N-doped graphene, with varying N content\nand doping modality, is utilized in the lithium–sulfur battery\nelectrolyte to address low ionic conductivity, lithium polysulfide\n(LiPS) shuttling, and Li anode instability. The study reveals that\nhigher N content and pyridinic N modality graphene in the electrolyte\npositively influence battery performance. The results are 2-fold:\nhigher overall N content improves capacity retention (73%) after 225\ncycles at 0.2 C, and pyridinic-type nitrogen demonstrates the best\nperformance at high C rates, exhibiting a 4-fold capacity increase\nrelative to the reference cell at 2 C. Further, the computational\nstudy validates the adsorption affinity of LiPS to pyridinic nitrogen\nand improved Li<sup>+</sup> mobility on the graphene backbone observed\nexperimentally. This first experimental study on the impact of N-dopant\nconcentration and modality on electrochemical performance provokes\ninsights into tailoring N functionalization to achieve superior electrochemical\nperformance.