Multishelled Hollow Spherical High Entropy Oxide as a Separator Modification Layer toward Stable Lithium–Metal Batteries

Lithium–metal batteries (LMBs) have received widespread publicity because of their preeminent energy density. However, lithium–metal anodes (LMAs) face abysmal problems including dendrite growth and violent interfacial side reactions, which sorely hinder further progress of LMBs. Here, a well-designed (CoZnNiMnFe)₃O₄ high entropy oxide with a multishelled hollow spherical shape (HHEO) is first developed as a functionalized layer to modify a commercial polypropylene (PP) separator (named as HHEO-PP). Based on high ionic conductivity and excellent electrolyte wettability, the HHEO-PP separator achieves fast Li⁺ diffusion and homogenized Li⁺ flux. Therefore, half cells and symmetric cells based on HHEO-PP obtain high Coulombic efficiency (CE) and long lifespan. Li||LiFePO₄ (Li||LFP) full cell including HHEO-PP stably circulates 1000 cycles with a CE of 99% at 2 C. These findings strongly testify the sterling performance of HHEO-PP and expand the path for high entropy oxide functionalized separators for other alkali metal batteries.