In a recent study published in Small, researchers introduced a three-dimensional, freestanding porous carbon nanofiber (PCNF) structure embedded with silicon oxide (SiOx), designed to address critical challenges in lithium-metal batteries (LMBs).
This engineered host aims to prevent dendrite formation while improving electrochemical stability, capacity retention, and overall battery safety.
The structure combines high surface area, excellent electrical conductivity, internal porosity, and strong lithium affinity to support uniform lithium-ion transport and deposition, an important step toward making lithium-metal batteries commercially viable.
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Background
Lithium-metal anodes offer high energy density but struggle with issues like dendrite growth due to lithium's high reactivity. These dendrites compromise battery safety and shorten cycle life. Traditional approaches—such as using liquid electrolytes or protective surface coatings—often fall short in delivering long-term stability.
Recent advancements have shifted toward designing structured hosts that guide lithium deposition more effectively. Among these, nitrogen-doped carbon materials stand out for their good conductivity, chemical stability, and tunable surface properties. Integrating silicon oxides (SiOx) into carbon frameworks improves their lithiophilicity and helps accommodate volume changes during cycling, which stabilizes lithium plating.
ZIF-8, a zeolitic imidazolate framework, is used as a precursor to build hollow, porous nanostructures through thermal treatment. Combining ZIF-8-derived carbon, SiOx, and nitrogen doping into a single host offers a synergistic approach: it supports uniform lithium deposition, curbs dendrite formation, and preserves structural integrity through repeated charging cycles. This multi-material strategy helps tackle the core limitations of conventional anode designs.
The Current Study
The team synthesized the 3D SiOx-embedded, nitrogen-doped porous carbon nanofibers (referred to as SiOx-1@PCNF-1200) using a stepwise fabrication process centered on electrospinning and thermal treatment.
The process began by creating a homogeneous solution of ZIF-8 polyhedra, tetraethyl orthosilicate (TEOS), polyacrylonitrile (PAN), and polystyrene (PS). ZIF-8 contributed hollow nanocages, TEOS supplied the SiOx, and PS acted as a sacrificial agent to introduce tubular pores.
This mixture was electrospun into continuous fibers under controlled conditions. Afterward, the fibers underwent pyrolysis at around 1200°C. This step carbonized the PAN, embedded SiOx throughout the structure, and converted ZIF-8 into nitrogen-doped carbon. Simultaneously, the PS decomposed to create internal channels within the fibers.
To confirm the structure, the team used scanning and transmission electron microscopy (SEM, TEM), BET surface area analysis, and X-ray diffraction (XRD). These techniques verified the presence of hierarchical porosity, uniform SiOx distribution, and an intact nanofiber framework.
For electrochemical testing, the composite host was evaluated in half-cell configurations using lithium metal as the counter electrode. Performance was measured in terms of Coulombic efficiency, cycling stability, rate capability, and electrochemical impedance spectroscopy (EIS). The team also assembled full cells using commercial cathodes like NCM622 and NCM811 to assess real-world applicability.
Results and Discussion
The resulting SiOx-embedded PCNFs exhibited a porous, interconnected tubular structure with nanocages distributed uniformly throughout the fibers. SEM and TEM images showed continuous, flexible fibers with pores along their length and at the nanoscale. BET analysis revealed a high specific surface area, particularly at the optimal carbonization temperature of 1200°C, supporting enhanced electrolyte infiltration and numerous lithium nucleation sites.
Electrochemical testing demonstrated that the composite host significantly outperformed conventional lithium hosts. EIS results showed low interfacial resistance, reflecting strong electronic conductivity and efficient lithium-ion transport. The internal porosity and SiOx embedding played key roles in ensuring uniform lithium plating, effectively eliminating dendrite formation, even under extended cycling.
In symmetric cells, the composite maintained high Coulombic efficiency and stable voltage over hundreds of cycles, confirming its excellent reversibility. It also supported high-capacity lithium plating (up to 5 mAh/cm²) with even distribution throughout the structure, including its internal pores, which is crucial for preventing dendrite intrusion.
When paired with commercial cathodes in full-cell setups, the anode demonstrated strong specific capacities, stable cycling, and robust rate performance. These results highlight how the structural design balances electrical conductivity, mechanical strength, and lithium affinity.
The hierarchical porosity enhances ion mobility and offers room for lithium expansion during cycling, while SiOx domains increase lithiophilicity and act as internal lithium reservoirs—both key to minimizing structural degradation and maintaining long-term performance.
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Conclusion
This study demonstrates that integrating porous, nitrogen-doped carbon nanofibers with embedded SiOx is an effective strategy for stabilizing lithium-metal anodes. By addressing dendrite growth, improving ion transport, and enabling high-capacity, long-life cycling, this composite host brings lithium-metal batteries a step closer to practical, commercial deployment.
Journal Reference
Nahm YW., et al. (2025). 3D Lithiophilic Freestanding Hosts with SiOx-Embedded Hierarchical Porous N-Doped Carbon Nanofibers for Dendrite-Free Lithium Metal Batteries. Small, 2504223. DOI: 10.1002/smll.202504223, https://onlinelibrary.wiley.com/doi/10.1002/smll.202504223