Superfine MnO2 Nanowires with Rich Defects Toward Boosted Zinc Ion Storage Performance.

Abstract

The core challenge of MnO2 as the cathode material of zinc-ion batteries remains to be their poor electrochemical kinetics and stability. Herein, MnO2 superfine nanowires (∼10 nm) with rich crystal defects (oxygen vacancies and cavities) are demonstrated to possess high efficient zinc-ion storage capability. Experimental and theoretical studies demonstrate that the defects facilitate the adsorption and diffusion of hydrogen/zinc for fast ion transportation and the build of a local electric field for improved electron migration. In addition, the superfine nanostructure could provide sufficient active sites and short diffusion pathways for further promotion of capacity and reaction kinetics of MnO2. Remarkably, the defect-enriched MnO2 nanowires manifest an energy density as high as 406 W h kg-1 and an excellent durability over 1000 cycles without noticeable capacity degradation. Mechanistic analysis substantiates a reversible coinsertion/extraction process of H+ and Zn2+ with a simultaneous deposition/dissolution of zinc sulfate hydroxide hydrate nanoflakes. This work could enrich the fundamental understanding of defect engineering and nanostructuring on the development of advanced MnO2 materials toward high-performance zinc-ion batteries.