Significantly improved Li-ion diffusion kinetics and reversibility of Li₂O in a MoO₂ anode: The effects of oxygen vacancy-induced local charge distribution and metal catalysis on lithium storage

Sluggish Li-ion diffusion kinetics and low initial coulombic efficiency (CE) are two big issues to be urgently solved for the MoO₂ anode. Herein, we achieve significantly improved Li-ion diffusion kinetics and reversibility of Li₂O in a MoO₂ anode by elaborately constructing oxygen vacancies and atomic-level spatial distribution of a Ni catalyst, therefore evidently boosting its rate behavior and initial CE. The oxygen vacancy and highly distributed metallic Ni modulation is achieved by finely controlling the annealing time. The density functional theory (DFT) calculations reveal that the creation of oxygen vacancies results in unbalanced charge distribution within MoO₂, thus inducing a foreign coulomb force to boost the Li-ion transfer. Furthermore, the metallic Ni in Ni/MoO_2-δ can perform as an effective catalyst to ensure the fully reversible conversion of the as-formed Li₂O, thereby increasing the initial CE. Benefiting from this multiscale coordinated design, Ni/MoO_2-δ displays high discharge capacity (1630.9 mA h g^-1 at 0.2 A g^-1), large initial CE (83.7%), and excellent rate capability, and outperforms most of the previously reported MoO₂-based anodes. Such a design concept not only brings MoO₂ one big step closer to practical application, but also can be extended to guide the design of other anode materials with high theoretical capacity.