Core-Shelled Low-Oxidation State Oxides@Reduced Graphene Oxides Cubes via Pressurized Reduction for Highly Stable Lithium Ion Storage

Metal oxides have been regarded as promising next-generation anode materials for rechargeable lithium ion batteries; however, their poor stability, which is caused by large volume changes during repeated lithiation/delithiation, remains a challenge. Here, conformally encapsulated low-oxidation state oxide cubes with reduced graphene oxide (RGO) obtained via a new pressurized reduction consisting of external mechanical compression and internal thermokinetic reduction from highly porous metal oxides/RGO aerogel (RGOA) are reported. Using single crystalline (SC) cobalt oxides and iron oxide cubes as model systems, the SC-Co₃O₄ or Fe₂O₃ cube/RGOA are pressurized into compacted xerogel along with a uniform thermokinetic reduction, which result in topotactic transformation to core-shelled CoO/RGO or Fe₃O₄@RGO cubes. The SC-CoO and SC-Fe₃O₄ cubes isolated perfectly in the RGO shells have dramatically improved their cycling stabilities for lithium ion storage to hundreds of times. The lithium-ion storage stability of the core/shelled low-oxidation state oxide/RGO cubes can be prolonged by at least 400 times.