리튬-황 전지의 기능성 중간층으로 그래핀과 Mo2C/Mo2N 나노입자로 구성된 나노섬유(Mo2C/Mo2N rGO NFs)를 사 용하였다. Mo2C/Mo2N 나노입자는 섬유 구조 내 고르게 분산되어 리튬 폴리설파이드의 화학적 흡착을 위한 활성 사이트 역할을 함으로써 전해질로의 용출을 효과적으로 억제하였다. 또한 구조 내 매트릭스로 구성된 그래핀 나노시트는 충방전이 진행되는 동안 이온 및 전자의 빠른 이동을 보장할 뿐만 아니라 반응 시 산화/환원 반응을 원활하게 하여 높은 리튬 폴리설파이드의 재사용을 보장하였다. 그 결과 Mo2C/Mo2N rGO NFs로 코팅된 분리막을 기능성 중간층으로 사용, 순수 황 전극(황 함량 70 wt%, 황 로딩 2.1 mg cm-2)으로 제작된 리튬-황 전지는 0.1 C에서 400회 충방전 후 476 mA h g-1의 안정적인 방전 용량을 나타냈으며, 1.0 C의 높은 전류밀도에서도 574 mA h g-1의 방전용량을 나타내었다. 본 연구에서 제안된 나노구조체 합성 전략은 고성능 리튬-황 전지 용 기능성 중간층 및 다양한 에너지 저장 소재분야로의 확장이 가능하다.

Nanofibers comprising reduced graphene oxide (rGO) and Mo2C/Mo2N nanoparticles (Mo2C/Mo2N rGO NFs) were prepared for a functional interlayer of Li-S batteries (LSBs). The well-dispersed Mo2C and Mo2N nanoparticles in the nanofiber structure served as active polar sites for efficient immobilization of dissolved lithium polysulfide. The rGO nanosheets in the structure also provide conductive channels for fast ion/electron transport during charging-discharging and ensured reuse of lithium polysulfide during redox reactions through a fast charge transfer process. As a result, the cell assembled with Mo2C/Mo2N rGO NFs-coated separator and pure sulfur electrode (70 wt% of sulfur content and 2.1 mg cm?2 of sulfur loading) showed a stable discharge capacity of 476 mA h g-1 after 400 charge-discharge cycles at 0.1 C. Furthermore, it exhibited a discharge capacity of 574 mA h g-1 even at a high current density of 1.0 C. Therefore, we believe that the proposed unique nanostructure synthesis strategy could provide new insights into the development of sustainable and highly conductive polar materials as functional interlayers for high performance LSBs.

Nanofiber Electrospinning Functional interlayer Cathodes Lithium-sulfur batteries

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