Bi-MOF-derived BiPS4/C armored with conductive Ni-HHTP: a dual MOF-mediated strategy for polysulfide suppression in sodium storage

Abstract

Metal phosphosulfides (MPS_x), especially BiPS₄, have emerged as promising anode candidates for sodium-ion batteries, distinguished by distinctive multinary redox chemistry, open tunnel-type structure, and high theoretical capacity (> 1000 mAh g⁻¹). However, their practical implementation is fundamentally limited by polysulfide dissolution/shuttling and structural instability during prolonged cycling. Herein, we develop a groundbreaking two-stage metal–organic framework (MOF)-engineered compositing strategy through which Bi-MOF-derived BiPS₄/C pillars are robustly armored with conductive Ni-HHTP (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) nanorods. Density functional theory calculations reveal that this design achieves dual functionality: increased carrier density for enhanced charge transport dynamics and effective polysulfide adsorption to inhibit dissolution. The fabricated BiPS₄/C@Ni-HHTP composite delivers remarkable electrochemical properties, including high initial charge/discharge specific capacities of 1063.6/1181.3 mAh g⁻¹ at 0.1 A g⁻¹ and outstanding long-term stability with 99.2% capacity retention after 2000 cycles at 2 A g⁻¹. Such superb performance stems from the perfect synergy of the inherent high-capacity redox behavior of BiPS₄, the buffering effect of MOF-derived carbon, and the conductivity, adsorption sites and mechanical resilience of Ni-HHTP. This work establishes a new design paradigm for MPS_x materials, demonstrating how to simultaneously overcome conductivity limitations and shuttle effects in conversion-type electrodes.