Phase separation-hydrogen etching-derived Cu-decorated Cu-Mn bimetallic oxides with oxygen vacancies boosting superior sodium-ion storage kinetics

Abstract

Understanding the crystal phase evolution of bimetallic oxide anodes is the main concern to profoundly reveal the conversion reaction kinetics and sodium-ion storage mechanisms. Herein, an integrated self-supporting anode of the Cu-decorated Cu-Mn bimetallic oxides with oxygen vacancies (Ov-BMO-Cu) are in-situ generated by phase separation and hydrogen etching using nanoporous Cu-Mn alloy as self-sacrificial templates. On this basis, we have elucidated the relationship between the phase evolution, oxygen vacancies and sodium-ion storage mechanisms, further demonstrating the evolution of oxygen vacancies and the inhibition effect of manganese oxides as an “anchor” on grain aggregation of copper oxides. The kinetic analyses confirm that the expanded lattice space and increased oxygen vacancies of cycled Ov-BMO-Cu synergistically guarantee effective sodium-ion diffusion and storage mechanisms. Therefore, the Ov-BMO-Cu electrode exhibits higher reversible capacities of 4.04 mA h cm−2 at 0.2 mA cm−2 after 100 cycles and 2.20 mA h cm−2 at 1.0 mA cm−2 after 500 cycles. Besides, the pre-sodiated Ov-BMO-Cu anode delivers a considerable reversible capacity of 0.79 mA h cm−2 at 1.0 mA cm−2 after 60 cycles in full cells with Na3V2(PO4)3 cathode, confirming its outstanding practicality. Thus, this work is expected to provide enlightenment for designing high-capacity bimetallic oxide anodes.