Li-air Battery with a Superhydrophobic Li-Protective Layer.

Li-air  batteries operated in ambient air are imperative toward real practical applications. However, the passivation of lithium metal anodes induced by attacking air hinders their long-term running, accelerating the degradation of Li-air batteries. Herein, a hydrogel-derived hierarchical porous carbon (HDHPC) layer with superhydrophobicity is proved as an effective Li-protective layer for a Li-air battery that suppresses the H2O attack and lithium dendrite formation during cycling. Accordingly, the HDHPC protective layer-based Li-air cell exhibits eminent cycling stability in ambient air [relative humidity (RH) of ∼40%], which is far better than that of the Li-air cell without the HDHPC protective layer. It is also demonstrated that the conversion of O2/Li2O2 in Li-air batteries adversely affects the decomposition of the byproduct and electrolyte. The usage of the HDHPC protective layer pioneers a new avenue of developing high-performance Li-air batteries in ambient air.