High Capacity and Reversibility of Oxygen‐Vacancy‐Controlled MoO3 on Cu in Li‐Ion Batteries: Unveiling Storage Mechanism in Binder‐Free MoO3−x Anodes

MoO3 has great potential as an electrode for lithium‐ion batteries due to its unique layered structure that can host Li+. Despite high theoretical capacity (≈1117 mAh g−1), MoO3 is not widely used simply because of poor rate capability due to lower electronic conductivity and severe pulverization. The Li‐storage mechanism in MoO3 is also still unclear. Herein, oxygen‐vacancy‐controlled MoO3 is used without any additional binders and conductive materials to directly examine the Li‐storage mechanism on MoO3−x. Li‐storage capacity based on the reversible formation/decomposition of solid‐electrolyte interphase (SEI) films and the transformation of MoO3−x to amorphous Li2MoO3 is demonstrated. The surfaces of MoO3−x are conjugated with Cu2O nanoparticles via annealing at 200 °C. Cu2O acts as an effective catalyst for the formation of SEI films and the reversible reaction of MoO3−x with Li+ ions. As a result, Cu2O@MoO3−x exhibits a charge capacity of 1100 mAh g−1 after the second cycle and maintains a high reversible capacity, whereas MoO3−x exhibits a charge capacity of 900 mAh g−1 and fades to 590 mAh g−1 after 100 cycles at 1 A g−1.