Gradient lithiation to load controllable, high utilization lithium in graphitic carbon host for high-energy batteries

Abstract

The multiphase interaction between Li metal and carbon materials provides great opportunities to design advanced composite anodes for Li metal batteries. Herein, we report the conversion of single-sheet graphitic carbon papers (CPs) to function-gradient Li/C composite anodes with controllable formations of LiC6 and Li metal through controlling the thermal infiltration time. The uniform and dense lithiophilic LiC6 is formed first and gradually covers the entire CP host, which promotes the subsequent homogeneous infiltration of metallic Li into the CP. The resulting composite anode has a unique gradient structure, with one example consisting of a lithiated LiC6 coating of 5.8 mAh cm−2 and a thin Li bottom layer of 2.7 mAh cm−2. Such a gradient composite structure allows for the selective utilization of Li metal and LiC6 as the active component under different electrochemical conditions. This composite anode, with a much leaner Li loading than many reported Li/C composite anodes, has a stable porous framework and abundant lithiophilic sites, which enables uniform local electric field and stable Li metal deposition during cycling. Paired with high-capacity cathodes, the composite anode, with only a fraction of Li metal loading compared to Li foil, can provide better long-term cycling stability, and higher rate capability.