高等学校化学研究 ›› 2021, Vol. 37 ›› Issue (2): 254-258.doi: 10.1007/s40242-021-0423-0
DOU Yaying1,2, ZHANG Yantao3, GUO Feng4, SHEN Yanbin5, CHEN Gang2, WEI Yingjin2, XIE Zhaojun1, ZHOU Zhen1
DOU Yaying1,2, ZHANG Yantao3, GUO Feng4, SHEN Yanbin5, CHEN Gang2, WEI Yingjin2, XIE Zhaojun1, ZHOU Zhen1
摘要: In view of the ever-growing pressure for green gas emission reduction, there is an urgent need for renewable energy systems. Rechargeable alkali metal-oxygen batteries, especially lithium-oxygen(Li-O2) batteries, are deemed the most promising energy storage systems because of their higher theoretical energy density than that of current lithium-ion batteries[1—5]. However, their practical application is seriously hindered by the active oxygen intermediates(O2-, LiO2, and 1O2) and the insulating Li2O2 product[6,7]. The former is destructive to carbon materials, and the latter is dependent on electrocatalysts or redox mediators[8—10]. Therefore, although carbon-based materials have many unique properties, such as high electronic conductivity, light mass and low cost, they are not practical air cathodes for Li-O2 batteries. Instead of forming peroxide species, potassium-oxygen(K-O2) and sodium-oxygen(Na-O2) batteries enable a single-electron redox process of M++O2+ e-←→MO2(M=K or Na). This provides an elegant strategy to enhance the oxygen reduction reaction(ORR) and oxygen evolution reaction(OER) kinetics, thereby greatly decreasing overpotential and improving round-trip efficiency(>90%) even without any electro-catalyst[11—15]. Obviously, it paves an exciting avenue to use carbon materials in metal-O2 batteries, which can significantly reduce the cost and further increase the energy density of batteries. Besides, the replacement of Li with abundant Na and K also makes large-scale implementation more feasible[16]. Unlike Na-O2 batteries, where the discharge products(NaO2, Na2O2, Na2O2·H2O, or mixtures) vary significantly with the operating conditions, KO2 with higher stability(ΔGr of KO2: