Co 3d orbital degeneracy elimination by one-step B/Te dual defects: Synergy of charge redistribution and enhanced d-orbital reactivity for flexible supercapacitors

Transition metal tellurides have restricted applications due to their sluggish reaction kinetics. Herein, we report a transformative strategy, namely the elimination of orbital degeneracy, to optimize charge distribution and enhance electron transfer efficiency for TMTes supercapacitors. A single-step process of dual-defect engineering—simultaneously introducing B doping (d B ) and Te vacancies (V Te )—enables the d B V Te -CoFeTe material to achieve fundamental improvements in structural stability and ion transport capability. Specifically, B doping induces alterations in the crystal structure, which in turn suppresses the dissolution of active materials and eliminates the degeneracy of the t 2g (d xy ,d yz ,d xz ) and e g (d z 2 ,d x 2 -y 2 ) orbital sublayer in the Co 3d orbitals, adjusting the spin state of Co 3+ from high spin to low spin—key mechanisms underlying the enhanced performance. Furthermore, the presence of Te vacancies provides additional active sites, and the synergistic effect of both enhances the pore structure and accelerates reaction kinetics. Consequently, d B V Te -CoFeTe demonstrates remarkable electrochemical performance and exceptional cycling stability, with a specific capacity of 996.2C g −1 at 1 A g −1 , and retains 92.3 % of its initial capacity after 10,000 cycles. This work provides a new direction for the development of high-performance energy storage devices. • One-step NaBH 4 doping to introduce B while simultaneously generating Te vacancies. • Interstitial B doping eliminates orbital degeneracy, shifting Co 3+ from HS to LS. • Defect engineering tunes crystal structure, boosting Te ion dissociation energy. • Assembled flexible supercapacitor shows superb mechanical and cycle stability.