Bimetallic MXene with tailored vanadium d-band as highly efficient electrocatalyst for reversible lithium-oxygen battery

The transfer of electrons from V to Ti in the Ti-C-V bond leads to an upward shift of the d-band center of V, which enhances the adsorption of V on the intermediate LiO2, fundamentally improving the electrocatalytic performance of TiVC. [Display omitted] Lithium-oxygen (Li-O2) battery possesses high theoretical energy density of ∼ 3500 Wh kg−1, yet the sluggish kinetics of oxygen redox reactions hinder its practical application. Herein, TiVC bimetallic MXene solid solution is prepared as the efficient electrocatalyst for Li-O2 battery. The results of experiment and theoretical calculations reveal that through the formation of Ti-C-V bond in TiVC, electrons transfer from V site to Ti site enhances electron delocalization of V sites, which causes the upshift of d band center of V site and strengthens the adsorption of intermediate products (LiO2) on TiVC electrode surface. Due to the strong adsorption of intermediates, the film-like Li2O2 can be formed on TiVC electrode via the surface-adsorbed pathway, which ensures the full contact between the electrode and discharged product and thus facilitates the charge transfer between TiVC electrode and oxygen species during charge process. As a consequence, the TiVC based Li-O2 battery exhibits superior electrochemical performance including large discharge capacity (12780 mAh/g) and extended cycling stability (422 cycles) at the current density of 300 mA g−1.