Suppressing Dendrite Growth of a Lithium Metal Anode by Modifying Conventional Polypropylene Separators with a Composite Layer

Lithium metal is a promising candidate anode for next generation high energy density batteries. However, the Li dendrite growth results in electrode degradation and safety hazards, obstructing its practical applications. Herein, we propose a facile and effective method to build a robust ion conductive layer on the lithium metal surface. A thin coating layer containing nano-Si and poly(acrylic acid) on the surface of the conventional separator would react with lithium metal after adding electrolytes, forming a protective layer composed of the Li-Si alloy and LiPAA, which is a good Li-ion conductor. Both the Li-Li symmetric and full cells (Li-LiFePO4 and Li-S) using this modified separator exhibited much better cycle stability than those using an unmodified one. The dendrite suppression and electrochemical performance enhancement should be attributed to the unique interfacial structure modification for uniform and accelerated Li+ flux and rich lithium deposition sites. These findings suggest that the lithium interfacial properties have a huge effect on lithium stripping/plating and that the proposed strategy would provide new insights toward high energy lithium metal batteries.