Tuning the electronic structure of GaN through F/B doping for enhanced Na/K storage: A DFT-based exploration

This study focuses on enhancing the intrinsic electron conductivity of GaN. An innovative approach employing F and B atomic doping strategies was adopted to construct two modified structures, that is, F-GaN and B-GaN. Their application potential in sodium/potassium-ion batteries was systematically investigated through first-principles calculations. First, analysis of the phonon spectrum dispersion curve confirmed the kinetic stability of F-GaN and B-GaN. Second, density of states calculations indicate that F-doping and B-doping significantly modulate the band structure of GaN, and the intrinsic bandgaps of F-GaN and B-GaN are 0.71 and 0.03 eV, respectively, which are much lower than that of pure GaN (1.54 eV), thus substantially enhancing electron conductivity. Meanwhile, F-GaN and B-GaN achieve lower ion diffusion barriers and faster ion diffusion kinetics. Besides, the differential charge density and Bader charge analysis confirm significantly enhanced charge transfer efficiency between F-GaN/B-GaN and Na+/K+, thereby boosting electrochemical activity between ions and the material. Finally, the binding energy and open-circuit voltage calculations show both F-GaN and B-GaN exhibit good adsorption stability, and possessing higher open-circuit voltages, demonstrating greater energy density potential. This study provides a theoretical basis for the rational design of GaN-based materials in alkali metal ion batteries.