Institute of Physical Chemistry, Justus-Liebig-University Giessen , Heinrich-Buff-Ring 58, 35392 Giessen, Germany.
ACS Appl Mater Interfaces. 2014 Aug 13;6(15):12083-92. doi: 10.1021/am5010943. Epub 2014 Jul 22.
Lithium peroxide (Li2O2), the solid and intrinsically electronic insulating discharge product of Li-O2 batteries strongly influences the discharge and charge kinetics. In a series of experiments, we investigated the growth of Li2O2 upon discharge and the corresponding reduction and oxidation processes by varying the depth of discharge. The results indicate that insulating Li2O2 particles with a disc-like shape were formed during the initial discharge stage. Afterward, the nucleation and growth of Li2O2 resulted in the formation of conducting Li2O2 shells. When the discharge voltage dropped below 2.65 V, the Li2O2 discs evolved to toroid-shaped particles and defective superoxide-like phase presumably with high conductivity was formed on the rims of Li2O2 toroids. Both Li2O2 and the superoxide-like phase are unstable in ether-based electrolytes resulting in the degradation of the corresponding cells. Nevertheless, by controlling the growth of Li2O2, the chemical reactivity of the discharge product can be suppressed to improve the reversibility of Li-O2 batteries.
过氧化锂（Li2O2）是 Li-O2 电池的固体和本征电子绝缘放电产物，强烈影响放电和充电动力学。在一系列实验中，我们通过改变放电深度研究了 Li2O2 在放电过程中的生长以及相应的还原和氧化过程。结果表明，在初始放电阶段形成了具有盘状的绝缘 Li2O2 颗粒。之后，Li2O2 的成核和生长导致了导电 Li2O2 壳的形成。当放电电压降至 2.65 V 以下时，Li2O2 圆盘演变为环形颗粒，并且在 Li2O2 环的边缘上形成了具有高导电性的缺陷超氧化物相。在醚基电解质中，Li2O2 和超氧化物相均不稳定，导致相应电池的降解。然而，通过控制 Li2O2 的生长，可以抑制放电产物的化学反应性，从而提高 Li-O2 电池的可逆性。
