Redox Mediator with the Function of Intramolecularly Disproportionating Superoxide Intermediate Enabled High‐Performance Li–O₂ Batteries

Abstract

The large charge overpotential and poor cycling stability triggered by sluggish Li2O2 oxidation kinetics and severe superoxide‐related side reactions greatly restrict the development and application of lithium–oxygen batteries. Finding out high‐efficiency catalysts that can effectively facilitate a highly reversible formation/decomposition of lithium peroxide is still a crucial challenge in the field of Li–O2 batteries. Herein, a soluble catalyst of 2,2'‐Azino‐bis(3‐ethylbenzothiazoline‐6‐sulfonic acid) diammonium salt (ABTS) that can promote highly reversible formation and decomposition of Li2O2 during discharge and charge processes is reported for the first time. During discharge, it can capture and couple two LiO2 intermediates via its sulfonate and ammonium ions, and induce the intramolecular disproportionation reaction to produce Li2O2 through ionic microenvironment, which not only prompts the solution‐phase growth of Li2O2, but also restricts the reactivity of LiO2 intermediate, thus significantly alleviating the electrode surface passivation issue and suppressing the superoxide‐related side reactions. During charge, it can quickly transport electrons between the electrode and Li2O2 by serving as a new kind of redox mediator (RM), thus greatly facilitating the Li2O2 oxidation kinetics. As a result, the Li–O2 batteries that incorporate ABTS exhibit outstanding electrochemical performance, low charge overpotential, high discharge capacity, and high cycling stability.

Stabilizing Li–O2 Batteries with Multifunctional Fluorinated Graphene

“…In summary, challenges faced by LOBs are not only the actual deficient capacity and active O 2 − intermediate but also the stability of the Li-metal anode. Many targeted efforts have been devoted to address these tough issues, such as (a) redox mediators (RMs), such as DBBQ, 10 FePc, 11 and ABTS, 12 are efficient approaches to boost discharge capacity of LOBs; (b) polydopamine, 13 BHT 14 and Ce(CF 3 SO 3 ) 3 15 serve as O 2…”

“…In summary, challenges faced by LOBs are not only the actual deficient capacity and active O 2 – intermediate but also the stability of the Li-metal anode. Many targeted efforts have been devoted to address these tough issues, such as (a) redox mediators (RMs), such as DBBQ, FePc, and ABTS, are efficient approaches to boost discharge capacity of LOBs; (b) polydopamine, BHT and Ce­(CF 3 SO 3 ) 3 serve as O 2 – scavengers or quenchers to alleviate O 2 – -derived side reactions; (c) alloy anode, artificial SEI, and electrolyte additives are considered as fascinating protection strategies for a Li-metal anode of LOBs. ,− However, fresh, modified strategies may simultaneously create intricate new issues, such as RMs’ involvement in undeniable side reactions with O 2 – and Li-metal. − Although the above related-solutions are feasible from a scientific aspect, a single strategy in previous works is unlikely to concurrently solve LOBs-related issues from engineering aspect.…”

2D SnSe Cathode Catalyst Featuring an Efficient Facet‐Dependent Selective Li2O2 Growth/Decomposition for Li–Oxygen Batteries

“…As shown in Figure S13a (Supporting Information), Li 2 O 2 (with a peak at 775 cm −1 ) was detected after being discharged. [54][55][56] In Figure S13b, the wide bands at 1000 and 1300 cm −1 are attributed to DMSO (δCH = 950 cm −1 , νSO = 1030 cm −1 , and δ S CH 3 = 1315 cm −1 ). [57,58] The fluctuate peaks at 450 cm −1 could be ascribed to Li 2 O 2 .…”

“…[59] Side products Li 2 CO 3 were also detected in Raman and FTIR tests which could result from the existence of carbon initiating the side reaction and also lead to the high charge overpotential and degradation of the electrode. [2,55,57] In situ differential electrochemical mass spectrometry (DEMS) and ex-situ XPS were used to probe the reaction kinetics on the SnSe catalyst in LOBs. Figure 3b and Figure S14 (Supporting Information) show the gas evolution rate for O 2 , CO 2 , and H 2 O under a constant current charging or discharging voltage distribution diagram at 500 mA g −1 within a time range of 2 h. In Figure S14 (Supporting Information), an evident oxygen consumption with a 2.06e − /O 2 process was observed during the discharge process, indicating that the formation of Li 2 O 2 is dominated during the ORR process.…”

RuO2-Incorporated Co3O4 Nanoneedles Grown on Carbon Cloth as Binder-Free Integrated Cathodes for Tuning Favorable Li2O2 Formation

“…In the past few years, researchers have devoted themselves to develop an efficient electrolyte–cathode contact interface to improve the electrochemical performance of LOBs. , In terms of structure, enlarging the electrolyte–cathode interface area can theoretically achieve higher discharge capacity of the battery. − A variety of novel cathode structures or composite electrolyte–cathode structures have been proposed to provide sites for the formation and decomposition of insoluble Li 2 O 2 , but this improvement cannot reduce the overpotential obviously. , On the other hand, noble metals, , transition metal oxides ,,, and soluble redox media − have been introduced into the cathode as catalysts to promote oxygen redox kinetics. ,− However, insoluble discharge products will cover the surface of the catalyst, resulting in discharge termination. , Obviously, this strategy cannot greatly increase the discharge capacity of the battery. Meanwhile, irreversible side reactions induced by decomposition of polymeric binders have become critical issues. , Therefore, in order to improve the application of electrolyte–cathode interfaces in LOBs, huge efforts were made to design a binder-free framework with large specific surface area and high catalytic activity which enables one to store and decompose enough discharge products, while ensuring sufficient transport channels for oxygen, lithium ions, and electrons. ,,− A free-standing cathode generally obtained by electrospinning, electrodeposition, or hydrothermal methods provides LOBs with enough storage space for Li 2 O 2 and a continuous mass transfer channel. ,− Typical of these published studies is growing acicular Co 9 S 8 nanorods directly onto the porous carbon foil to store plenty of discharge production and achieve superior bifunctional catalytic properties …”