Surfaces/Interfaces Modification for Vacancies Enhancing Lithium Storage Capability of Cu₂O Ultrasmall Nanocrystals

Theoretically, Cu2O delivers a poor Li storage capacity ∼373.9 mA h g–1 based on a so-called conversion reaction (Cu2O + 2Li → 2Cu + Li2O). Herein, we broke through the bottleneck and acquired an impressive lithium storage capability (1122 mA h g–1) tripled more than the theoretical one by an in situ surface/interface engineering process for the first time. The surface/interface modification enabled us to fabricate ultrasmall nanocrystals of Cu2O with Cu vacancies (VCu) of high concentration, somewhat like monovalent anion doping. Except for the conversion reaction-type capacity, VCu enhancing intercalation pesudocapacitance in Cu2O and its reduction product-Cu also contributed a lot to the Li-storage capability. First-principles calculation substantiated that intercalation energy of Li was severely lowered for both Cu vacancy-rich Cu2O and Cu comparing with their stoichiometric counterparts. Another important factor for the enhancement was the surface/interface organic species themselves which could reversibly store Li by redox reactions. The surface/interface modification for vacancies, vacancy inheritance from metal oxide to single metal, and vacancy-enhancing Li-storage capability in metal oxide and single metal all will inspire us a lot in fabricating new-generation advanced electrodes for rechargeable batteries.