Redox Reaction and Dissolution Analysis for Hollow <i>C</i> Nanospheres Comprising <i>N</i> ‐Doped <i>C</i> Framework With Abundant Ni–Co Heteronuclear Catalysts for Highly Durable K‒Te Batteries

ABSTRACT Tellurium (Te), emerging as a promising alternative to sulfur (S) and selenium (Se), offers significant advantages for potassium (K) ion storage due to its comparable theoretical volumetric capacity (2619 mAh cm −3 ) and higher electronic conductivity (∼10 2 S m −1 ), which promotes rapid charge transfer and improves reaction kinetics. However, substantial volume changes during potassiation/depotassiation and the shuttling effect of polytellurides hinder the feasibility of K–Te batteries. Moreover, comprehensive studies on the phase formation and dissolution mechanism of K‐polytellurides (K–pTe n ) employing various in situ and ex‐situ techniques are scarcely reported. Herein, we introduce a rational strategy utilizing nickel (Ni) and cobalt (Co) heteronuclear double‐atom catalysts (DACs) encapsulated within hollow porous carbon nanospheres (Ni/Co‒N‒HPCNS) as hosts for tellurium impregnation (Te‒Ni/Co‒N‒HPCNS). In situ and ex‐situ XRD analysis revealed continuous phase transformation during discharge from amorphous Te (starting at OCV) to K 2 Te 3 (discharged to 1.5 V) and finally to K 5 Te 3 (discharged to 0.5 V). During the reverse scan, K 5 Te 3 was reversibly converted to K 2 Te 3 (charged to 3.0 V). Additionally, density functional theory calculations have shown that the presence of Ni/Co‒DAC significantly impedes the dissolution of K–pTe n species, thereby expediting the reaction kinetics to unprecedented levels (3000 cycles at 2.0C). When tested as a negative electrode for K‐ion storage in a full‐cell layout, the prepared nanostructure exhibits highly reversible K‐ion redox reactions, demonstrating its potential for commercial applications. We believe that the comprehensive design and characterization strategy discussed herein will open new frontiers for obtaining nanostructures with unparalleled electrochemical performances.