Unveiling the Electro‐Chemo‐Mechanical Failure Mechanism of Sodium Metal Anodes in Sodium–Oxygen Batteries by Synchrotron X‐Ray Computed Tomography
Xia Zhang, Shenghang Zhang, Jie Lu, Fengcheng Tang, Kang Dong, Zhenjiang Yu, André Hilger, Markus Osenberg, Henning Markötter, Fabian Wilde, Shu Zhang, Jingwen Zhao, Gaojie Xu, Ingo Manke, Fu Sun, Guanglei Cui
Abstract
Abstract Rechargeable sodium–oxygen batteries (NaOBs) are receiving extensive research interests because of their advantages such as ultrahigh energy density and cost efficiency. However, the severe failure of Na metal anodes has impeded the commercial development of NaOBs. Herein, combining in situ synchrotron X‐ray computed tomography (SXCT) and other complementary characterizations, a novel electro‐chemo‐mechanical failure mechanism of sodium metal anode in NaOBs is elucidated. It is visually showcased that the Na metal anodes involve a three‐stage decay evolution of a porous Na reactive interphase layer (NRIL): from the initially dot‐shaped voids evolved into the spindle‐shaped voids and the eventually‐developed ruptured cracks. The initiation of this three‐stage evolution begins with chemical‐resting and is exacerbated by further electrochemical cycling. From corrosion science and fracture mechanics, theoretical simulations suggest that the evolution of porous NRIL is driven by the concentrated stress at crack tips. The findings illustrate the importance of preventing electro‐chemo‐mechanical degradation of Na anodes in practically rechargeable NaOBs.