Mesoporous β-MnO2 Air Electrode Modified with Pd for Rechargeability in Lithium-Air Battery

The electrochemical performance and electrode reactions using ordered mesoporous β - MnO 2 modified with Pd as a cathode catalyst for rechargeable Li-air batteries was reported. Well-ordered mesoporous β-MnO 2 was prepared using mesoporous silica KIT-6 as a template under hydrothermal synthesis of Mn(NO 3 ) 2 ·H 2 O. The obtained mesoporous β-MnO 2 shows narrow pore size distribution of 1 nm. With the dispersion of small amounts of Pd to β-MnO 2 , mesoporous β-MnO 2 exhibited a high initial discharge capacity of 817 mAh/g -cat. with high reversible capacity. Charging potential is suppressed at 3.6 V vs. Li/Li + , which is highly effective for preventing the decomposition of organic electrolyte. The mesoporous β-MnO 2 /Pd electrode shows good rate capability and cycle stability. Ex-situ and in-situ XRD results suggested that the observed capacity comes primarily from the oxidation of Li + to Li 2 O 2 followed by Li 2 O after discharge to 2.0 V vs. Li/Li + . Electron spin resonance measurements suggest that the formation of superoxide anion radicals contributs to the oxidation of Li + and the radicals were recovered during charge. Ex-situ FTIR measurement suggested that no electrolyte decomposition was observed and no Li 2 CO 3 was formed during discharge when ethylene carbonate (EC)-diethyl carbonate (DEC) (3:7), which is highly stable for Li-air battery, was used as the electrolyte.