Gelatin Nanosphere‐Decorated 3D Aramid Nanofiber Hybrid Nanoporous Separators with Regulated Ion Transport for Li‐Metal Batteries

ABSTRACT High‐porosity nanoporous separators exhibit fast ion conduction and homogeneous Li ⁺ ion distribution, which are advantageous for effective dendrite suppression in Li‐metal batteries. However, their controlled fabrication of highly porous nanostructures in thin film form remains challenging. Hence, the present study reports on the phase‐separation‐induced self‐assembly of highly porous 3D aramid nanofiber (ANF) separators decorated with gelatin nanospheres (GNFs) for use in Li‐metal batteries. During this process, the gelatin nanospheres are spontaneously self‐assembled onto the ultraporous ANF matrix in order to minimize interfacial energy. The resulting nanoporous GNF separator exhibits high porosity (> 60%) along with preferential affinity toward PF ₆ ⁻ anions, thereby achieving a high Li ⁺ cation conductivity (σ ⁺ ) of 0.69 mS/cm. Notably, this conductivity is 4 times greater than that of commercial Celgard and 28 times greater than that of the gelatin‐free ANF sample. The enhanced ionic conductivity and homogeneous ion distribution promote effective dendrite suppression for Li‐metal anodes by the formation of stable solid electrolyte interphase layers. Resultantly, Li half cells with GNF separators show improved cycling stability, low overpotentials, and high coulombic efficiency. The Li/LiNi _0.8 Co _0.1 Mn _0.1 O ₂ full cell exhibits enhanced cycle performance even at 4.5 V, further enabled by the transition‐metal ion capture capability from the gelatin nanospheres.