β-MnO2 nanorods with exposed tunnel structures as high-performance cathode materials for sodium-ion batteries

Abstract

Sodium-ion batteries are being considered as a promising system for stationary energy storage and conversion, owing to the natural abundance of sodium. It is important to develop new cathode and anode materials with high capacities for sodium-ion batteries. Herein, we report the synthesis of β-MnO2 nanorods with exposed tunnel structures by a hydrothermal method. The as-prepared β-MnO2 nanorods have exposed {111} crystal planes with a high density of (1 × 1) tunnels, which leads to facile sodium ion (Na-ion) insertion and extraction. When applied as cathode materials in sodium-ion batteries, β-MnO2 nanorods exhibited good electrochemical performance with a high initial Na-ion storage capacity of 350 mAh g−1. β-MnO2 nanorods also demonstrated a satisfactory high-rate capability as cathode materials for sodium-ion batteries. β-MnO2 nanorods with exposed tunnel structures have been successfully synthesized by a hydrothermal method. The as-prepared β-MnO2 nanorods have exposed {111} crystal planes with a high density of (1 × 1) tunnels, leading to facile Na-ion insertion and extraction. When applied as cathode materials in Na-ion batteries, the β-MnO2 nanorods exhibited a superior electrochemical performance with a high initial Na-ion storage capacity of 350 mAh g−1.β-MnO2 nanorods also demonstrated an excellent high rate capability and a good cyclability. Sodium-ion batteries are promising alternatives to their lithium-ion counterparts for stationary energy storage and conversion. Sodium is more abundant than lithium, resulting in cheaper rechargeable batteries. However, this gain is coupled to lower densities and cyclabilities, leading researchers to focus on finding appropriate materials for electrodes. Guoxiu Wang and co-workers from Australia and South Korea have now prepared a cathode material with exposed tunnel structures that demonstrates good performances. Nanorods of β-MnO2 — a form of manganese dioxide — make attractive components for cathodes owing to their tunnel structure, which favors the storage and transport of sodium ions. Through a hydrothermal synthesis— whereby chemical precursors are heated in aqueous solution—Wang and colleagues fabricated nanorods with specific crystallographic faces (111) exposed. When these nanorods were used as battery cathodes, the team observed a high initial sodium storage capacity as well as the facile insertion and extraction of sodium ions.