New Reaction Pathway of Superoxide Disproportionation Induced by a Soluble Catalyst in Li‐O₂ Batteries

Abstract

Aprotic Li‐O2 battery has attracted considerable interest for high theoretical energy density, however the disproportionation of the intermediate of superoxide (O2−) during discharge and charge leads to slow reaction kinetics and large voltage hysteresis. Herein, the chemically stable ruthenium tris(bipyridine) (RB) cations are employed as a soluble catalyst to alternate the pathway of O2− disproportionation and its kinetics in both the discharge and charge processes. RB captures O2− dimer and promotes their intramolecular charge transfer, and it decreases the energy barrier of the disproportionation reaction from 7.70 to 0.70 kcal mol−1. This facilitates the discharge and charge processes and simultaneously mitigates O2− and singlet oxygen related side reactions. These endow the Li‐O2 battery with reduced discharge/charge voltage gap of 0.72 V and prolonged lifespan for over 230 cycles when coupled with RuO2 catalyst. This work highlights the vital role of superoxide disproportionation for Li‐O2 battery.

Promoted Reaction Reversibility by Dual-Effect 15-Crown-5 Ether Additive for High-Performance Li–O2 Batteries

“…Li 1s and O 1s XPS of the CNT cathodes were performed to further determine the composition of the discharge product (Figure S10). The discharge products are Li 2 O 2 and Li 2 CO 3 for both electrolytes with and without 15C5, which is different from the XRD results. However, the proportion of Li 2 CO 3 in discharge products with DMSO + LiNO 3 + 15C5 is lower than that with DMSO + LiNO 3 , indicating that the side reaction is effectively retarded by the crown ether additive.…”

Superoxide Radical Capture Agent for a Stable and Efficient Li-CO2 Battery: Experimental and Density Functional Theory Studies

“…Subsequently, DMSO would engage in the reaction with HOO • and Li + , leading to the emergence of DMSO 2 byproducts. 15 The reactions occurring between O 2…”

“…Subsequently, a reduced discharge/charge voltage gap of 0.72 V and an improved cycle life have been obtained for the lithium−oxygen battery with an RB cation. 15 In addition, acetylacetone iridium(III) [Ir(acac) 3 ] has been demonstrated as a multifunctional soluble catalyst to accelerate the electrochemical oxygen reaction. The oxygen reduction reaction pathway and the reactivity of O 2…”

“…Based on previous research, when the electrolyte solvent dimethyl sulfoxide (DMSO) is attacked by O 2 •– , DMSO would be stripped of an H atom by O 2 •– initially, resulting in the formation of HOO • . Subsequently, DMSO would engage in the reaction with HOO • and Li + , leading to the emergence of DMSO 2 byproducts . The reactions occurring between O 2 •– and organic solvents or additives within the electrolyte result in electrolyte oxidation and consumption, thereby leading to an increased overpotential, inferior cycling stability, and shortened cycle life. , Alongside, the irreversible oxidative parasitic reactions of O 2 •– with electrode materials cause the accumulation of byproducts, altering the structure and composition of electrodes, which eventually lead to sluggish discharge/charge kinetics, large impedance, and capacity degradation. , Additionally, the reaction between O 2 •– and Li metal leads to the formation of lithium peroxide or lithium peroxide ions, which is a potential hazard to battery safety and longevity. ,,− …”

“…It demonstrates that the RB cation shows a positive impact on the discharge/charge process of batteries, while simultaneously mitigating the side reactions associated with the O 2 •– and singlet oxygen. Subsequently, a reduced discharge/charge voltage gap of 0.72 V and an improved cycle life have been obtained for the lithium–oxygen battery with an RB cation . In addition, acetylacetone iridium­(III) [Ir­(acac) 3 ] has been demonstrated as a multifunctional soluble catalyst to accelerate the electrochemical oxygen reaction.…”