Ligand Engineering‐Enhanced Catalytic Activity of Octanuclear Zn(II)−Siloxane Clusters for Advanced Lithium–Sulfur Batteries

Octanuclear Zn(II)−siloxane−PhPz nanoclusters are surgically sculpted into the octanuclear Zn(II)−siloxane−BiPhPz clusters (OZSBPC) configuration through ligand engineering, where each ligand in OZSBPC is adorned with an appended benzene ring. Benefitting from the electronic and molecular modulation effect of benzene rings, the reinforced electrical conductivity, sulfur loading capacity, and adsorption characteristics are endowed to the OZSBPC, ultimately achieving the optimization of lithium−sulfur catalytic performance.

Abstract

Polynuclear metal clusters (PMC) with atomically defined architectures exhibit unique electrochemical catalytic behaviors in lithium−sulfur battery (LSB). Nevertheless, the precise fabrication of PMC with tailored configurations, and a comprehensive understanding of their structure-dependent property evolution, remains a formidable challenge. Herein, ligand engineering is employed to upgrade octanuclear Zn(II)−siloxane−PhPz clusters by grafting one more benzene ring onto azopyrazole ligand to form octanuclear Zn(II)−siloxane−BiPhPz clusters (OZSBPC). An integrated investigation combining kinetic analyses, in situ characterizations, and theoretical calculations reveals that the introduction of biphenyl moieties enlarges the intrinsic cavity to host more sulfur species, while the conjugation-enhanced ligand framework facilitates more efficient electron transfer. Moreover, the enhanced nucleophilicity at nitrogen sites and the upshifted d-band center synergistically strengthen the affinity toward polysulfides via π−π conjugation interactions. Consequently, the catalytic efficiency of OZSBPC undergoes a substantial enhancement, thereby enabling the assembled Ah-class Li−S pouch cell delivers a peak energy density of 504 Wh kg_total ⁻¹, and sustains stable cycling at 429 Wh kg_total ⁻¹ for 40 cycles. Moreover, stable operation over 150 cycles is achieved under −33 °C. Our study makes a breakthrough in precisely constructing PMC and in optimizing the performance via progressive structure upgrading, which made a landmark impact on lithium−sulfur catalytic chemistry.

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