Synergistic Catalysis by Single‐Atom Catalysts and Redox Mediator to Improve Lithium–Oxygen Batteries Performance

Abstract

to low round-trip efficiency as well as limited capacity. And cathode clogging arising from insulated, insoluble discharge products accumulation blocks the electron transfer and oxygen/Li + diffusion, resulting in a high overpotential for the electrochemical reactions, which will trigger parasitic reactions such as electrolyte oxidation. [5] As cathode corrosion aggravates, the batteries deliver poor cycle stability.Over the past few decades, numerous studies have intensively focused on cathodes and catalysts to address the main challenges in the Li-O 2 batteries. [6][7][8][9][10][11][12] Single atom materials with superior catalytic properties and unique electronic structure are promising electrode materials for Li-O 2 batteries. [13][14][15][16][17][18][19] Single atoms serving as catalytic centers effectively promote the slow kinetic process of lithium oxygen batteries. [20] However, the catalysis of immobile single-atom catalysts is limited only for Li 2 O 2 particles directly deposited on the surface of the catalysts without oxidizing the electronically isolating Li-peroxide layers, which leads to low round-trip efficiency and poor cycle stability. [21][22][23] To address this concern, many attempts have been made to effectively promote the decomposition of Li 2 O 2 . Recently, redox mediators, a kind of liquid catalysts have been developed for facilitating the oxidation of Li 2 O 2 upon charging. [24,25] The redox mediators will first be oxidized in solution phase to form oxidized species during charge process, followed by chemically oxidizing the Li 2 O 2 from the solution side so that the catalytic effect can be exerted on all the Li 2 O 2 that is formed during the ORR process. [26] Lithium bromide (LiBr) was first proposed by Sun and coworkers as a RM in Li-O 2 batteries to reduce the OER overvoltage. [27] Br − can be oxidized upon charging at 3.48 V to Br 3 − and further be oxidized to Br 2 at 4.0 V, both of which can readily react with Li 2 O 2 to form Br − , Li + , and O 2 . [28,29] However, undesirable shuttle phenomenon, that is Br 2 or Br 3 − diffuse to and react with Li anode, resulting in the poor cycle stability and round-trip efficiency. [26] Herein, we report the successful combination of single-atom cobalt anchored in porous N-doped hollow carbon spheres Lithium-oxygen (Li-O 2 ) batteries with ultrahigh theoretical energy density have attracted widespread attention while there are still problems with high overpotential and poor cycle stability. Rational design and application of efficient catalysts to improve the performance of Li-O 2 batteries is of significant importance. In this work, Co single atoms catalysts are successfully combined with redox mediator (lithium bromide [LiBr]) to synergistically catalyze electrochemical reactions in Li-O 2 batteries. Single-atom cobalt anchored in porous N-doped hollow carbon spheres (CoSAs-NHCS) with high specific surface area and high catalytic activity are utilized as cathode material. However, the potential performances of batteries are difficult to...

Hollow microstructural regulation of single-atom catalysts for optimized electrocatalytic performance

“…Qiu et al [115] discovered the influence of the dimensionality of the graphene matrix on the formation of Fe SACs [Figure 5]. They revealed that single-shell hollow graphene spheres play a critical role in the preparation of single Fe atom catalysts.…”

Water-Induced Surface Reconstruction of Co3O4 on the (111) Plane for High-Efficiency Li–O2 Batteries in a Hybrid Electrolyte

“…Lithium peroxide is an insulator with a wide band gap, and its conductivity is poor, which leads to the inability of electrons to be transmitted timely, causing large polarization of the battery. In addition, Li 2 O 2 and the reaction intermediate LiO 2 both have high reactivity and are prone to react with the electrolyte to generate side reaction products, resulting in a decrease in the cycle life of the battery. − It will be of great significance to develop non-Li 2 O 2 -based LOBs. Besides Li 2 O 2 , LiOH, LiO 2 , and even Li 2 O are also other reported reversible discharge products that are obtained by controlling catalysts and optimizing electrolyte systems. , Inspired by these works, we utilized the synergistic effect on the Co 3 O 4 (111) plane to enhance the electrochemical performance of LOBs in water-added electrolytes.…”

Engineering Metal Alloy Nanocrystals Anchored on N‐Doped Nanoporous Carbon for Li‐O2 Batteries

“…However, the development of LOBs is still hindered by several challenges, such as the limited cycle life, low discharge specific capacity, and poor rate performance, which are mainly due to the sluggish kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) at the oxygen cathodes [4–6] . Therein, Li + reacts with the oxygen to form the eventual Li 2 O 2 product during the discharging process, which decomposes to the Li + and oxygen in the subsequent charging process [7–11] . The major discharge product Li 2 O 2 , which is intrinsically insulating and insoluble in the electrolyte, is deposited on the cathode surface and further causes the degradation of the LOBs [12–15] .…”

“…[4][5][6] Therein, Li + reacts with the oxygen to form the eventual Li 2 O 2 product during the discharging process, which decomposes to the Li + and oxygen in the subsequent charging process. [7][8][9][10][11] The major discharge product Li 2 O 2 , which is intrinsically insulating and insoluble in the electrolyte, is deposited on the cathode surface and further causes the degradation of the LOBs. [12][13][14][15] To data, although some precious metals along with their oxides (Pt, Ru, IrO 2 , RuO 2 ) have shown excellent ORR and OER performance, they cannot be produced in a large scale due to the high cost and low reserve.…”