Li₂O₂ Formation Electrochemistry and Its Influence on Oxygen Reduction/Evolution Reaction Kinetics in Aprotic Li–O₂ Batteries

Abstract

Aprotic Li–O2 batteries are regarded as the most promising technology to resolve the energy crisis in the near future because of its high theoretical specific energy. The key electrochemistry of a nonaqueous Li–O2 battery highly relies on the formation of Li2O2 during discharge and its reversible decomposition during charge. The properties of Li2O2 and its formation mechanisms are of high significance in influencing the battery performance. This review article demonstrates the latest progress in understanding the Li2O2 electrochemistry and the recent advances in regulating the Li2O2 growth pathway. The first part of this review elaborates the Li2O2 formation mechanism and its relationship with the oxygen reduction reaction/oxygen evolution reaction electrochemistry. The following part discusses how the cycling parameters, e.g., current density and discharge depth, influence the Li2O2 morphology. A comprehensive summary of recent strategies in tailoring Li2O2 formation including rational design of cathode structure, certain catalyst, and surface engineering is demonstrated. The influence resulted from the electrolyte, e.g., salt, solvent, and some additives on Li2O2 growth pathway, is finally discussed. Further prospects of the ways in making advanced Li–O2 batteries by control of favorable Li2O2 formation are highlighted, which are valuable for practical construction of aprotic lithium–oxygen batteries.

Sacrificial Co-solvent Electrolyte to Construct a Stable Solid Electrolyte Interphase in Lithium–Oxygen Batteries

“…8−11 Also, the formation mechanism of discharge products on the cathode surface has been well studied. 12 However, a stable electrolyte is indispensable for LOBs. However, there are still many problems with the commonly used electrolyte, which is decomposed by radical superoxides (O 2…”

Enhancing the Reaction Kinetics and Reversibility of Li–O2 Batteries by Multifunctional Polymer Additive

“…[38][39][40] In addition, a discrepancy of discharge voltage plateau in Figure 2d (TF: 2.75 V, base: 2.69 V) further indicates that reaction kinetics is significantly enhanced in PTFEMAcontained Li-O 2 cell during ORR process. Taking the reaction mechanism of ORR process into consideration (Figure S10, Supporting Information), [9,14] we propose that the ORR kinetics acceleration in the presence of PTFEMA is not only related to the homogeneous Li + flux at the cathode side but also concerned with the superoxide intermediate species (O 2 − and LiO 2 ) during ORR process. For attractive electrostatic equilibrium force, the uniform and coordinated Li + with PTFEMA readily reacts with O 2 − to reduce the lifetime of O 2 − and generate PTFEMA-LiO 2 complexes.…”

“…Nonconductive Li 2 O 2 product is a serious obstacle for fast and homogeneous electronic and Li + flux transportation during ORR/OER process, which accordingly causes sluggish ORR/OER electrochemical reaction kinetics of LOBs. [5,[8][9][10] Particularly, the inhomogeneous and concentrated accumulation of Li 2 O 2 further exacerbates the severity of ORR/OER slow dynamics. On the cathode side, the depressed and poor reaction kinetics of ORR/OER process can directly cause unsatisfying As a potential candidate for next-generation energy storage systems, Li-O 2 batteries (LOBs) with their attractive theoretical energy density have triggered great interest.…”

Strategies toward anode stabilization in nonaqueous alkali metal–oxygen batteries

“…But the insoluble and insulating Li 2 O 2 has sluggish kinetics during charge and discharge processes, which leads to a high charge overpotential and bad battery performance. 2 The reactions are shown below: 3,4…”