Modeling of an aprotic Li-O2 battery incorporating multiple-step reactions

This paper reports on a one-dimensional lithium-oxygen (Li-O-2) battery model incorporating the competitive uptake of discharge intermediate between the electrode surface and the aprotic electrolyte. Unlike previous models, in which a single-step reaction is assumed for aprotic Li-O-2 batteries (2Li(+) + 2e(-) + O-2 -> Li2O2), the present model more realistically depicts the electrochemical process in a battery system by taking account of multiple-step reactions, including the surface reduction reactions of adsorbed oxygen (Li+ O-2* e(-) -> LiO2*) and adsorbed superoxide (LiO2* + Li+ e(-) -> Li2O2) along with the dissolution of superoxide into electrolyte. Transient and spatial analyses are performed to identify the limiting steps for the battery's performance, including oxygen transport and final discharge product precipitation. The effects of the kinetics of oxygen reduction reaction and superoxide dissolution are also investigated. In addition, the impact of cathode microstructures on the battery's performance is studied. It is found that the electrolyte's ability to dissolve the discharge intermediate (LiO2) is critically important to improve the discharge capacity. (C) 2016 Elsevier Ltd. All rights reserved.