Performance of Air Electrode Catalysts in the Presence of Redox Mediators for High-Capacity Li–O₂ Batteries

Abstract

Lithium–oxygen batteries (LOBs) have usually been investigated at low current densities and low areal capacities due to small amounts of active materials supported on carbon papers, though they theoretically have high energy density. In addition, studies on catalysts have usually been conducted in the absence of redox mediators. In this study, we have investigated various catalysts at a high current density (0.4 mA cm–2), at a high areal capacity (4 mAh cm–2), and in the presence of dual redox mediators (RMs) of NO3 – and Br–, using Ketjen black free-standing sheets (KBFSs; thickness: 270 μm) of high areal weight (6 mg cm–2). The RMs reduced the charge overvoltage even in the presence of catalysts, and catalysts also promoted Li2O2 decomposition in the presence of RMs. RuO2/KBFS, Ir-Co/N-KBFS, and Co/KBFS improved both cyclability and overvoltages compared with KBFS. RuO2/KBFS and Ir-Co/N-KBFS decomposed Li2CO3 at lower voltages than KBFS and exhibited less Li2CO3 residue after charge than KBFS. However, catalysts were coated with byproducts even in the presence of RMs during the discharge/charge tests.

A lithium–air battery and gas handling system demonstrator

“…46,47 It is known that H 2 O can be tolerated at greater levels than originally thought, and can even be beneficial. 42,48 Some progress has also been made in understanding the impact of LiOH and Li 2 CO 3 within metal–air cells, 35,49–51 but further optimisation is required for operation in air.…”

Research and Development of Novel Secondary Batteries in Japan

“…While promising, these approaches suffer from several fundamental and technical problems. The VSI reports significant achievements for the Mg-metal batteries in developing new electrolytes and electrode active materials through collaboration between material scientists and computational scientists in Japan. − The VSI describes extensive studies on the elucidating mechanisms of oxygen electrode reaction, developing electrode materials and solvents, and establishing cell design strategies for the practical implementation of Li–O 2 batteries. − …”