Preparation and electrochemical performance of ultra-thin reduced graphene oxide/lithium metal composite foils

Ultra-thin (≤50 μm) lithium metal anodes (LMAs) are highly desirable for high energy density lithium metal batteries (LMBs). However, their fabrication is complicated and costly due to the sticky and brittle nature of metallic Li, and they have a worse cycling stability than their thick counterparts. We report the fabrication of ultra-thin reduced graphene oxide/Li metal (rGO/Li) composite foils with thicknesses ranging from 10 to 50 μm. During the fabrication, disordered rGO sheets and molten metallic Li were stirred and combined at 200 ºC to produce micrometer-thick rGO/Li sheets, which were processed to form an ultra-thin uniform composite foil. The rGO sheets were randomly distributed in the rGO/Li composite to form a three-dimensional network, which is different from the laminated rGO structure previously reported, and supported stable Li plating/stripping behavior. As expected, a superior electrochemical performance was achieved using this composite sheet for the anode. A 50 μm-thick rGO/Li composite foil electrode displayed stable cycling for > 1 600 h at 1 mA cm−2 and 1 mAh cm−2 in symmetrical cells in an ether-based electrolyte. A full cell consisting of a 50 μm-thick rGO/Li composite foil anode and a sulfurized polyacrylonitrile cathode had a high capacity retention of 675 mAh g−1 after 220 cycles at 0.2 C.