Lithium metal electrode protected by stiff and tough self-compacting separator

Lithium metal anode (LMA) has exceptionally high capacity and low redox potential. However, lack of stable separator/solid electrolyte that can suppress morphological instabilities of LMA has significantly hampered its use. While high-stiffness solid electrolyte is regarded as a solution to suppress LMA sinusoidal wave instability, the poor toughness and failure tolerance often lead to cracking-based mechanical failures. Here, a facile surface spray of initially loose Sb2O3 powders on Li metal generates a self-compacting separator (SCS) in situ of 5 +/- 2 mu m thickness. Electrochemical characterization reveals that such SCS layer allows fast ion migration (10(-4) S cm(-1)) and is electronically insulating, causing Li to precipitate underneath stably and uniformly. Moreover, mechanical examination demonstrates that the SCS is stiff (>10 GPa modulus), tough, and possesses flexibility and self-healing ability. Protected by a SCS, LMA can cycle at 10 mA cm(-2)/10 mAh cm(-2) for 260 h without short-circuiting. When the ultrathin Li@SCS foil (total thickness 20 mu m) is paired against LiFePO4 cathode with <1.2 x excess Li, it demonstrates stable cycling for 60 cycles at an industrial loading of 3 mAh cm(-2) and a rate of 0.5C, tripling the cycle life compared to unprotected Li. The SCS-covered LMA is also nonflammable in fire for 180s in contrast to unprotected Li foil.