Zou Xiaohong, Cheng Zhichao, Lu Qian, Liao Kaiming, Ran Ran, Zhou Wei, Shao Zongping
State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemical Engineering, Nanjing Tech University, No. 5 Xin Mofan Road, Nanjing 210009, China.
WA School of Mines: Minerals, Energy and Chemical Engineering (WASM-MECE), Curtin University, Perth, Washington 6102, Australia.
ACS Appl Mater Interfaces. 2021 Nov 17;13(45):53859-53867. doi: 10.1021/acsami.1c15349. Epub 2021 Nov 3.
Redox mediators (RMs) have become a significant point in the now-established Li-O battery system to reduce the charging overpotential in the oxygen evolution process. Nevertheless, a major inherent barrier of the RM is the redox shuttling between the Li metal anode and mobile RM, resulting in the corrosion of Li and depletion of RM. In this study, taking iodide/triiodide as a model RM, we propose an effective strategy by immersing the Li metal anode in I steam to create a 1.5 μm thick surface protective layer. The resultant ionic conductive LiI layer on the Li metal anode can not only suppress Li dendrite growth but also act as a buffer layer between the RM and bare Li. By combining the iodide/triiodide RM with the LiI protective layer, the Li-O battery shows low and steady charge voltage plateaus of ∼3.6 V over 70 cycles. Importantly, the symmetrical cell using the LiI-protected Li electrode exhibited small Li plating/stripping overpotentials (∼20 mV, 480 h), far superior to that of the bare Li electrode (∼70 mV, 300 h). The interfacial observation shows that dendrite growth on the Li metal can be effectively suppressed by optimizing the LiI protective layer.
氧化还原介质（RMs）已成为当前成熟的锂氧电池系统中降低析氧过程充电过电位的一个重要因素。然而，RM的一个主要固有障碍是锂金属阳极与可移动RM之间的氧化还原穿梭，导致锂的腐蚀和RM的消耗。在本研究中，以碘化物/三碘化物作为模型RM，我们提出了一种有效的策略，即将锂金属阳极浸入碘蒸汽中以形成一个1.5μm厚的表面保护层。在锂金属阳极上形成的离子导电碘化锂层不仅可以抑制锂枝晶生长，还可以作为RM与裸锂之间的缓冲层。通过将碘化物/三碘化物RM与碘化锂保护层相结合，锂氧电池在70个循环中显示出约3.6V的低且稳定的充电电压平台。重要的是，使用碘化锂保护锂电极的对称电池表现出小的锂电镀/剥离过电位（约20mV，480小时），远优于裸锂电极（约70mV，300小时）。界面观察表明，通过优化碘化锂保护层可以有效抑制锂金属上的枝晶生长。
