3D Lithiophilic Freestanding Hosts with SiOx-Embedded Hierarchical Porous N-Doped Carbon Nanofibers for Dendrite-Free Lithium Metal Batteries

초록

3D host materials are promising for Li-metal anodes (LMAs) because of their adaptability to volume changes and large areas that prevent current localization, hindering dendritic Li formation. Herein, freestanding porous N-doped carbon nanofibers (PCNFs) with uniformly distributed SiOx are synthesized by electrospinning and subsequent carbonization. In these composites, tunnel-like, open channels are formed between the CNFs by removing polystyrene (PS) and the hollow N-doped nanocages (HNC) generated from zeolitic imidazolate frameworks-8 (ZIF-8) during carbonization, providing sufficient space for Li deposition. Accompanying these structural advantages, the adequate electron conductivity and lithophilic properties derived from the conductive N-doped CNFs and insulating SiOx confer optimized characteristics for uniform Li distribution. The coulombic efficiency exceeds 98% over 160 cycles in asymmetrical cells at a current density of 2.0 mA cm-2, with stable voltage hysteresis and an average overpotential of 25 mV for 1350 h in symmetrical tests. Full cells assembled with composite anodes predeposited with Li exhibited excellent capacity retention, delivering 141 mAh g-1 at 2.0 C with LiNi0.6Co0.2Mn0.2O2 (NCM622) cathodes. The results highlight that the optimized combination of conductive CNFs, HNCs, and insulating SiOx effectively enables uniform Li deposition, significantly enhancing cycling stability and Coulombic efficiency (CE) of LMAs.

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