Facile Synthesis of MnO₂/MWCNTs via UV Photolysis as High-Performance and Low-Cost Cathodes for Aqueous Magnesium Ion Batteries

For simple and fast synthesis of a high-performance electrode material for an aqueous magnesium ion battery (AMIB), UV photolysis is applied to prepare the binder-free δ-MnO2/multiwalled carbon nanotube (δ-MnO2/MWCNTs) composite on carbon cloth (CC). The MnO2 nanosheets are directly grown on the surface of CC covered by MWCNTs to form three-dimensional hierarchy construction, which enhances the electrochemical property. The δ-MnO2/MWCNT composite delivers a discharge capacity of 313.2 mA h g–1 at 50 mA g–1 and its capacitance retention at 1000 mA g–1 is near to 100% after 500 cycles. The AMIB system is assembled using δ-MnO2/MWCNTs as a cathode and VO2 as an anode, which displays a charge capacity of 108.4 mA h g–1 at 50 mA g–1. Furthermore, XPS and ex situ X-ray diffraction measurements are carried out to research the reaction mechanism of Mg ion insertion/deinsertion from δ-MnO2 during the electrochemical process. This work provides insights into the synthesis of the high-performance and low-cost electrode material for AMIB systems.