Quantum Capacitance Enhancement of AlN Nanoribbon Via Transition Metal Doping: Density Functional Study

First-principles density-functional calculations are used to explore the influence of transition-metal dopants (Sc, Ti, V, Mn, Fe, Co) on the electronic structure, stability and quantum capacitance (QC) of zig-zag AlN nanoribbons. Substitutional doping at either the edge or center of the ribbon is found to introduce mid-gap states that markedly increase the density of states near the Fermi level, yielding up to a 40-fold enhancement in QC related to the pristine lattice. Vanadium-doped configurations possess the highest cohesive energy (−5.85 eV per atom) and the largest surface-charge density (40 µC cm⁻² at +0.6 V vs −0.6 V), identifying them as optimal anode materials. Conversely, cobalt-rich ribbons deliver superior cathodic capacity, whereas Mn-doped systems exhibit almost symmetric charge storage. Phonon spectra confirm dynamic stability for all considered dopants. The results provide quantitative design rules for tailoring of AlN nanoribbons as high-rate, high-capacity electrodes in advanced supercapacitors.