La/Fe Co-doped CoO as a bifunctional material for supercapacitors and lithium-sulfur batteries: Synergistic regulation of hubbard u/band width and surface basic active sites

La 3+ /Fe 2+ co-doping tailors U and W of CoO for bulk electronic optimization. • La 3+ -induced distortion reconstructs Lewis base sites to suppress shuttle effect. • Base sites show strong Li + adsorption and weaken S-S bonds via electron injection. • As supercapacitor cathode: 1405.6 F g −1 at 1 A g −1 , device energy 93.0 Wh kg −1 . • As Li-S sulfur host: 1161.6 mAh g −1 at 0.1 C, 62.1% retention after 100 cycles. This work develops La/Fe co-doped cobalt oxide (La/Fe-CoO) as a bifunctional electrode material to simultaneously enhance the electrochemical performance of supercapacitors and lithium-sulfur batteries, targeting the common bottlenecks of sluggish charge transport and poor surface reaction kinetics. The performance limitations of CoO arise primarily from its unfavorable electronic structure parameters: excessive Hubbard repulsion energy ( U ) and narrow band width ( W ), which severely restrict redox efficiency and electron conductivity. To address these issues, La 3+ and Fe 2+ co-doping is employed to achieve precise synergistic regulation of U and W . Fe 2+ doping constructs an extended “Co 3d -O 2p -Fe 3d ” orbital hybridization network that broadens W , optimizes charge transport pathways, and substantially improves intrinsic conductivity. Meanwhile, La 3+ reduces the effective Hubbard U through f-d orbital coupling, weakening intraorbital electron repulsion and lowering the reaction barrier. More importantly, the large ionic radius of La 3+ induces local lattice distortion, generating abundant electron-rich Lewis basic active sites on the material surface, which are distinctly different from the Lewis acidic sites commonly reported in the literature. Unlike acidic sites based on metal cations, these basic sites not only immobilize polysulfides by electrostatically adsorbing Li + ions, but also inject electrons into the S-S antibonding orbitals, exerting a redox catalytic effect that promotes S-S bond cleavage and accelerates polysulfide conversion kinetics, thereby effectively suppressing the shuttle effect in lithium-sulfur batteries. This work, through the synergistic design of bulk electronic structure ( U / W ) modulation and surface basic site reconstruction, offers a feasible strategy for developing high-performance bifunctional electrode materials for energy storage applications. Download: Download high-res image (412KB) Download: Download full-size image