Improving the cycle life and failure resistance of lithium metal anodes is critical for next-generation rechargeable batteries. Here, we show that treating Li metal foil electrodes with ultrathin (∼2 nm) Al2O3 layers using atomic layer deposition (ALD) without air exposure can prevent dendrite formation upon cycling at a current density of 1 mA/cm2. This has the effect of doubling the lifetime of the anode before failure both under galvanostatic deep discharge conditions and cyclic plating/stripping of symmetric Li–Li cells. The ALD treated electrodes can be cycled for 1259 cycles before failure occurs, which is attributed to improved electrode morphology resulting from homogeneous Li ion flux across the electrode/electrolyte interface. Read Paper