Hierarchical α-MnO2 nanowires as an efficient anode material for rechargeable lithium-ion batteries

Abstract

In this work, a bulk quantity of α-MnO₂ hierarchical nanowires was synthesized by a facile redox reaction between potassium permanganate (KMnO₄) and glycine under ambient conditions. The physicochemical characterization results revealed that the MnO₂ sample exhibited highly uniform (1D) nanowire morphology and unique surface texture features such as a high specific surface area of 181 m² g⁻¹ with a beneficial mesoporous structure. Taking the advantage of hierarchical 1D nanowires morphology and improved microstructural properties, a cell with MnO₂ nanowires as an anode showed relatively good electrochemical performance with enhanced lithiation degree and improved cycling stability. The initial discharge capacity of as high as 1373 mA h g⁻¹ was achieved at 100 mA g⁻¹ and rendered a reversible capacity of 735 mA h g⁻¹ even after 100 cycles with an average Coulombic efficiency of 97%. The improved electrochemical performance of α-MnO₂ is attributed to its hierarchical nanowire morphology and enriched textural surface properties, which provide a good Li-ion diffusion path, large electrode–electrolyte contact area and effective accommodation of the strain generated from volume expansion during repeated lithiation/delithiation processes.