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Na‐O2 batteries are attractive for energy storage due to their high theoretical energy density. In order to alleviate Na dendrite formation, artificial protective coatings have been widely investigated in Na‐metal batteries (NMBs). Although it can be intuitive to expect transferable Na protection methodologies from NMBs to Na‐O2 batteries, the performance of anode protection coatings in Na‐O2 batteries remains obscure, because Na‐O2 batteries undergo a unique reaction mechanism involving superoxide. Here, the effect of superoxide crossover on the polymeric Na protection layer in Na‐O2 batteries is revealed, and an effective strategy to eliminate the implications of a superoxide‐sensitive protecting layer is proposed. Using polymeric alucone protected Na anode as an example, the alucone layer actually decomposes under superoxide attack and is incapable of facilitating long‐term cycling of Na‐O2 batteries in sharp contrast to its stable performance in NMBs. By blocking superoxide crossover with solid‐state electrolytes (SSEs), significantly improved Na‐O2 cell performance is demonstrated, recovering the Na dendrite suppressing effect of the alucone film. Benefiting from the synergistic effect of SSE and alucone layer, Na‐O2 batteries can achieve a long life of 325 cycles at 0.2 mA cm−2. This work indicates that the stability of the Na protection layer against superoxide should be taken into serious consideration. [ABSTRACT FROM AUTHOR]

Although metallic lithium is regarded as the "Holy Grail" for next‐generation rechargeable batteries due to its high theoretical capacity and low overpotential, the uncontrollable Li dendrite growth, especially under high current densities and deep plating/striping, has inhibited its practical application. Herein, a 3D‐printed, vertically aligned Li anode (3DP‐VALi) is shown to efficiently guide Li deposition via a "nucleation within microchannel walls" process, enabling a high‐performance, dendrite‐free Li anode. Moreover, the microchannels within the microwalls are beneficial for promoting fast Li+ diffusion, supplying large space for the accommodation of Li during the plating/stripping process. The high‐surface‐area 3D anode design enables high operating current densities and high areal capacities. As a result, the Li–Li symmetric cells using 3DP‐VALi demonstrate excellent electrochemical performances as high as 10 mA cm−2/10 mAh cm−2 for 1500 h and 5 mA cm−2/20 mAh cm−2 for 400 h, respectively. Additionally, the Li–S and Li–LiFePO4 cells using 3DP‐VALi anodes present excellent cycling stability up to 250 and 800 cycles at a rate of 1 C, respectively. It is believed that these new findings could open a new window for dendrite‐free metal anode design and pave the way toward energy storage devices with high energy/power density. [ABSTRACT FROM AUTHOR]