High Capacity and Reversibility of Oxygen‐Vacancy‐Controlled MoO 3 on Cu in Li‐Ion Batteries: Unveiling Storage Mechanism in Binder‐Free MoO 3− x Anodes

MoO 3 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 ), MoO 3 is not widely used simply because of poor rate capability due to lower electronic conductivity and severe pulverization. The Li‐storage mechanism in MoO 3 is also still unclear. Herein, oxygen‐vacancy‐controlled MoO 3 is used without any additional binders and conductive materials to directly examine the Li‐storage mechanism on MoO 3− x . Li‐storage capacity based on the reversible formation/decomposition of solid‐electrolyte interphase (SEI) films and the transformation of MoO 3− x to amorphous Li 2 MoO 3 is demonstrated. The surfaces of MoO 3− x are conjugated with Cu 2 O nanoparticles via annealing at 200 °C. Cu 2 O acts as an effective catalyst for the formation of SEI films and the reversible reaction of MoO 3− x with Li + ions. As a result, Cu 2 O@MoO 3− x exhibits a charge capacity of 1100 mAh g −1 after the second cycle and maintains a high reversible capacity, whereas MoO 3− 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 .