Electrolytic construction of nanosphere‐assembled protective layer toward stable lithium metal anode

The uncontrolled dendrite growth and electrolyte consumption in lithium metal batteries result from a heterogeneous and unstable solid electrolyte interphase (SEI). Here, a high‐voltage forced electrolysis strategy is proposed to stabilize the lithium metal via electrodepositing a spherical protective layer. This peculiar SEI is composed of a nanosized Li sphere that is encased with adjustable composition, as proved by cryo‐transmission electron microscopy and multiple surface‐sensitive spectroscopies. Such a three‐dimensional nanosphere‐assembled protective layer has homogeneous components, mechanical strength, and rapid Li‐ion conductivity, enabling it to alleviate the volume expansion and prevent dendrite growth during Li deposition. The symmetric cell can be stably operated for ultralong‐term cycling time of 2000 and 800 h even at high current densities of 1 and 10 mA cm−2, respectively. Using this interface permits stable cycling of full cells paired with LiFePO4 and LiNi0.8Co0.1Mn0.1O2 cathodes with low negative/positive capacity ratio, high current density, and limited Li excess. This tactic also fosters a novel insight into interface design in the battery community and encourages the practical implementation of lithium metal batteries. The uncontrolled dendrite growth and electrolyte consumption in lithium metal batteries result from an unstable and heterogeneous solid electrolyte interphase (SEI). Here, a high‐voltage forced electrolysis strategy is proposed to stabilize the Li surface by electrodepositing a spherical protective layer. The obtained nanosphere‐assembled protective layer has homogeneous components, mechanical strength, and rapid Li‐ion conductivity, enabling it to alleviate the volume change and suppress the dendrite growth during the Li plating/stripping. The symmetric cell can be stably operated for an ultralong‐term cycling time of 800 h even at ultrahigh current densities of 10 mA cm−2.