Dichalcogenide Electronegativity Engineering Enables Low‐Redox‐Potential Organic Anodes for High‐Performance Calcium‐Ion Batteries

Abstract

ABSTRACT Organic anodes for calcium‐ion batteries (CIBs) generally rely on extended conjugated structures to host high‐density redox couples for enhanced capacity. However, this design often lowers frontier molecular orbital energies, resulting in undesirably high redox potentials (> −0.6 V) that compromise cell voltages. Here we propose a dichalcogenide electronegativity engineering by introducing a family of diphenyl dichalcogen compounds (Ph‐2S, Ph‐2Se, and Ph‐2Te) featuring dual sulfide, selenide, telluride motifs, as high‐performance CIB anodes. The decreasing electronegativity along dichalcogenide bonds (S─S > Se─Se > Te─Te) progressively elevates the lowest unoccupied molecular orbital energy from −2.80 (Ph‐2S) to −2.50 (Ph‐2Se) and −2.00 eV (Ph‐2Te), shifting the redox potentials to increasingly negative values of −0.76, −0.82, and −0.84 V, respectively. Moreover, Ph‐2Te shows the strongest redox activity to start four‐electron Te‐conversion with 98% utilization (vs. 65% of Ph‐2Se and 31% of Ph‐2S). Consequently, Ph‐2Te anode liberates the highest capacity of 257 mAh g −1 , outperforming Ph‐2S (152 mAh g −1 ) and Ph‐2Se (223 mAh g −1 ). Notably, Ph‐2Te anode enables state‐of‐the‐art CIBs with a high redox voltage (1.2 V), an active‐material‐pair level energy density (68 Wh kg −1 ), and a long lifespan (5000 cycles). This work establishes dichalcogenide engineering as a promising strategy toward low‐redox‐potential organic anodes for advanced CIBs.