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.