Phenol‐Catalyzed Discharge in the Aprotic Lithium‐Oxygen Battery

Abstract

Discharge in the lithium‐O2 battery is known to occur either by a solution mechanism, which enables high capacity and rates, or a surface mechanism, which passivates the electrode surface and limits performance. The development of strategies to promote solution‐phase discharge in stable electrolyte solutions is a central challenge for development of the lithium‐O2 battery. Here we show that the introduction of the protic additive phenol to ethers can promote a solution‐phase discharge mechanism. Phenol acts as a phase‐transfer catalyst, dissolving the product Li2O2, avoiding electrode passivation and forming large particles of Li2O2 product—vital requirements for high performance. As a result, we demonstrate capacities of over 9 mAh cm−2 areal, which is a 35‐fold increase in capacity compared to without phenol. We show that the critical requirement is the strength of the conjugate base such that an equilibrium exists between protonation of the base and protonation of Li2O2.

High capacity surface route discharge at the potassium-O2 electrode

“…However, both KO2 and alkali peroxides are considered insulating, although debate exists in the literature regarding the conductivity of KO2, and both have little or no solubility in this solvent. [20,32,33] We note that the effect can also be observed in other solvents such as dimethyl sulfoxide (DMSO) and diethylene glycol dimethyl ether (diglyme), Figure S3. By holding at a low potential to drive reduction of O2 to K2O2, very similar amounts of capacity were consumed to form the surface film, suggesting the products in three solvents had very similar conductivities.…”

Promoting Li–O2 Batteries With Redox Mediators

“…The effect of acids is more complicated, with weak and strong acids showing different performances . Although H 2 O and acid improve the discharge capacity and rate capability, it is likely to result in more side reactions and reduce the chemical yield of Li 2 O 2 on discharge.…”

“…H 2 Oa nd some protic moleculeso ft he phenol family,f or example, phenol,2 ,6-di-tert-butyl-hydroxytoluene (BHT) have recently received interest. [17] They have no redoxc enter and cannot operate as redox shuttles or redox mediators, but they do somehow increaset he discharge capacity and current density and exhibit similar effects as RM disch .T he influence of H 2 Oh as been extensively studied;h owever,i ts effect has not been fully understood. [17d, 18] Considering there is an equilibrium between Li 2 O 2 and H 2 O 2 in the presenceo fw ater [Eq.…”

DABCOnium: Ein effizienter und Hochspannungs‐stabiler Singulett‐Sauerstoff‐Löscher für Metall‐O2‐Zellen

“…PeDTFSI ist amphoter, am tertiären N Lewis‐basisch und am quaternären N sauer, was möglicherweise das LiO 2 ‐Intermediat in Lösung bringen könnte. Schwierigkeiten, Zellen mit Zusätzen, die einen Lösungsmechanismus begünstigen, wieder aufzuladen, sind weithin anerkannt und die erschwerte Wiederaufladung unter Bedingungen, die den Lösungsprozess begünstigen, wurde ähnlich begründet . Es gibt daher weitgehend Übereinstimmung, dass man Mediatoren benötigt, um solche Zellen vollständig zu laden …”