Positive Electrode Passivation by Side Discharge Products in Li–O2 Batteriesстатья
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Дата последнего поиска статьи во внешних источниках: 23 декабря 2020 г.
Аннотация:The development of high specific energy Li−O2batteries faces a problem of poor cycling as a result of passivationof the positive electrode by both the discharge product (Li2O2)and side products (Li2CO3, etc.). The latter are the result ofoxidation of the electrode materials or electrolyte componentsprimarily by discharge intermediate superoxide anions (O2−) and,in less degree, by Li2O2. We report cyclic voltammetry studies ofthe electrode passivation in different relatively stable solvents. Wefound that slower passivation is observed for the electrolytes basedon high donor number solvents or solvents with high viscosity.Moreover, such behavior is reproduced for three different electrodematerials [glassy carbon (GC), TiC, and TiN] that pinpoints theprimary role of different oxygen reduction reaction mechanisms (Li2O2 surface deposition or solution growth) influenced by Li+ solvation energy and solvent viscosity. The chemistry of interaction between LiO2/Li2O2 and the electrode/solvent turns out to be less important. Additionally, we found that, for the electrode made of GC and TiN in all electrolyte solutions, the passivation by side products suppresses oxygen reduction after a certain number of cycles. In contrast, for TiC after several cycles, further passivation does not happen as a result of the formation of a thin and stable TiO2 layer in high donor number solvents.