Oxygen vacancy-expedited ion diffusivity in transition-metal oxides for high-performance lithium-ion batteries

Rapid capacity decay and inferior kinetics are the vital issues of anodes in the conversion reaction for lithium-ion batteries. Vacancy engineering can efficiently modulate the intrinsic properties of transition-metal oxide (TMO)-based electrode materials, but the effect of oxygen vacancies on electrode performance remains unclear. Herein, abundant oxygen vacancies are in situ introduced into the lattice of different TMOs (e.g., Co3O4, Fe2O3, and NiO) via a facile hydrothermal treatment combined with calcination. Taking Co3O4 as a typical example, results prove that the oxygen vacancies in Co3O4−x effectively accelerate charge transfer at the interface and significantly increase electrical conductivity and pseudocapacitance contribution. The Li-ion diffusion coefficient of Co3O4−x is remarkably improved by two orders of magnitude compared with that of Co3O4. Theoretical calculations reveal that Co3O4−x has a lower Li-insertion energy barrier and more density of states around the Fermi level than Co3O4, which is favorable for ion and electron transport. Therefore, TMOs with rich vacancies exhibit superior cycling performance and enhanced rate capability over their counterparts. This strategy regulating the reaction kinetics would provide inspiration for designing other TMO-based electrodes for energy applications.