Dual‐Functioning Molecular Carrier of Superoxide Radicals for Stable and Efficient Lithium–Oxygen Batteries

Abstract

Low round‐trip efficiency and poor cycle stability remain the major challenges associated with lithium–oxygen (Li–O2) batteries. These issues are primarily triggered by or correlated to the radical species produced during the operation of Li–O2 cells, which lead to significant deterioration of the electrolytes and air electrodes. Regulation of the reactivity of these radical species would thus open up opportunities to suppress such side reactions. Herein, a dual‐functioning molecule that is capable of mitigating the reactivity of radical species produced in a Li–O2 cell by reversibly forming stable intermediate complex during both the discharge and charge processes is introduced. Specifically, 5,5‐dimethyl‐1‐pyrroline N‐oxide (DMPO) is exploited, which has been widely used as a chemical agent to detect oxygen radicals, to induce the reversible formation of an intermediate complex, DMPO–O2−, in the presence of superoxide radicals. It is demonstrated that DMPO mediates the O2−‐involved electrochemical reaction, leading to significant suppression of side reactions and a remarkably improved oxygen efficiency. Unexpectedly, it is also observed that upon charging, DMPO actively scavenges the superoxides from the surface of discharge products, thus substantially lowering the charging overpotential. The combined radical mediation and scavenging of superoxides result in cycle stability of a practical Li–O2 cell over 200 cycles with a specific capacity of 1000 mAh g−1. The findings indicate the importance of controlling the reactivity of radical species and suggest a new pathway toward the realization of stable and efficient Li–O2 batteries.

Progress and Prospects in Redox Mediators for Highly Reversible Lithium–Oxygen Batteries: A Minireview

“…Kang and co-workers introduced a molecular carrier, 5-dimethyl-1-pyrroline N -oxide (DMPO), to regulate the reactivity of oxygen species . After O 2 – is electrochemically produced, DMPO would capture it to form an intermediate complex, DMPO–O 2 – , which promotes discharge (Figure c).…”

“…Panels a and b were reprinted with permission from ref . Copyright 2019 Wiley-VCH Verlag GmbH & Co. Panel c was reprinted with permission from ref . Copyright 2020 Wiley-VCH Verlag GmbH & Co. Panel d was reprinted with permission from ref .…”

“…Kang and co-workers introduced a molecular carrier, 5dimethyl-1-pyrroline N-oxide (DMPO), to regulate the reactivity of oxygen species. 74 75 For LiOH decomposition, our group proposed an excellent Super P composite electrode decorated by Ru and MnO 2 nanoparticles (Ru/MnO 2 /Super P). 76 With the catalytic effect of the Ru/MnO 2 /Super P electrode, the overpotential of charge was remarkably lowered to 0.21 V. Thus, the cyclic life was improved to 200 cycles under a current density of 500 mA g −1 , and the corresponding total voltage gap was approximately 0.32 V. The detailed mechanism is shown below (Figure 7d).…”

Acceleration of Singlet Oxygen Evolution by Superoxide Dismutase Mimetics in Lithium–Oxygen Batteries

“…These results are contrary to those of the previous paper that when 0.5 M DMPO is used, it can reversibly act as CRM and SODm for 100 cycles. [22] Also, DMPO has no stability against 1 O 2 , so DMPO cannot be used as reversible additive for LOBs (Figure S9c, Supporting Information). Therefore, DMPO and AQ were excluded from the screening materials for further experiments.…”

The use of amino-based functional molecules for the controllable synthesis of noble-metal nanocrystals: a minireview

“…[1][2][3][4] Thus, establishing effective and sustainable energy conversion and storage systems is extremely important for mankind. Renewable-energy conversion/storage devices, such as fuel cells, [5][6][7][8][9][10] water electrolysis devices, [11][12][13][14][15] and rechargeable metal-air batteries, [16][17][18][19][20] have attracted widespread attention due to their environmental friendliness, low carbon emissions, and good device safety. Currently, noble-metal-based materials, such as Pt-, Pd-, Ru-, and Ir-based catalysts, are common catalysts for energy-related catalytic reactions, [21][22][23][24] including the alcohol oxidation reaction, formic acid oxidation reaction (FAOR), oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and hydrogen oxidation reaction (HOR).…”