An ion-released MgI2-doped separator inducing a LiI-containing solid electrolyte interphase for dendrite-free Li metal anodes

Lithium metal batteries are among the strong contenders to satisfy the ever-increasing needs of energy storage systems, which however suffer from poor composition of the solid electrolyte interphase (SEI) layer and uncontrolled Li dendrites formation. In this regard, we report on the design of an ion-released MgI2-doped polyacrylonitrile (PAN) based nanofiber (MPANF) separator, which can lead to conducive SEI layer and dendrite-free Li anode. The combination of the lithophilic MgI2 nanoparticles with polarized PAN matrix comprehensively functions as a high-compatible interpenetrating network to homogenize ionic transportation and confront dendrite growth. The released I ions introduce the high-ion-conductivity LiI into SEI layer, which could induce the formation of favorable and protective interface layer in the early stage, as embodied in the enrichment of advantageous components such as LiNxOy, Li2O, LiF, and Li3N. Profited from the high-affinity MPANF separator, the Li||Li symmetric cell achieves an ultra-low voltage hysteresis of 46 mV with an extended lifespan of 580 h. And a prolonged lifetime of 590 cycles with an enhanced specific capacity of 140.1 mAh g−1 and the Coulombic efficiency of 96.2% at 1 C can be obtained in full cells. This work may offer a facile and high-affinity alternative to traditional polymeric separators for high-performance and dendrite-free Li metal batteries.