A one-pot microwave-assisted non-aqueous sol-gel approach to metal oxide/graphene nanocomposites for Li-ion batteries

Abstract

Non-aqueous sol-gel routes are elegant approaches for the synthesis of nanomaterials such as metal oxide nanocrystals and ordered organic-inorganic hybrid materials. These routes involving the reaction of metal oxide precursors in organic solvents (e.g. benzyl alcohol) at moderate temperature and pressure, offer advantages such as high crystallinity of the as synthesized oxides, high purity, high reproducibility and the ability to control the crystal growth without the need of additional ligands. Moreover, non-aqueous sol-gel is particularly suitable for one-pot synthesis of multi-metal and doped oxide materials. Microwave synthesis has recently shown several important advantages compared to traditional heating for the synthesis of inorganic nanomaterials by soft chemistry. In particular, the benzyl alcohol route greatly benefits from microwave heating by decreasing the reaction time to just a few minutes for nanoparticle formation, suppressing side reactions and improving the yield. In this thesis, a one-pot non-aqueous synthesis of crystalline SnO2- and Fe3O4-based graphene heterostructures in just few minutes for Li-ion battery applications is introduced. Here, the combined properties of the microwave heating and the benzyl alcohol route allow to selectively grow metal oxide nanoparticles at the surface of graphene oxide, which is reduced during synthesis. The as-fabricated nanostructures show good lithium intercalation-deintercalation performances at high rate and good cycling stability compared to the separate nano-building blocks.

본 연구에서는 리튬 이온 전지의 음극제로 사용하기 위해 마이크로웨이브를 열원으로 하여 비가수성 졸-겔 반응을 통한 산화 주석, 자철석과 리튬 이온 이차 전지의 전극으로서 이상적인 성질을 가지고 있다고 알려져 있는 그라핀-금속 산화물(산화주석, 자철석)혼합체를 원팟으로 합성하였다. 여기서 마이크로웨이브 가열과 벤질 알코올 경로의 특성이 결합되어 그라핀 옥사이드 표면 위에서 금속 산화물이 선택적으로 형성될 수 있었다. 그리고 리튬 이온 이차 전지의 음극으로서 성능 시험을 통하여 단순히 금속 산화물만 있을 경우보다 향상된 주기 성질과 높은 전류 속도에서도 안정적으로 용량을 유지하는 것을 확인하였다.