Bidirectional Lithiophilic Gradients Modification of Ultralight 3D Carbon Nanofiber Host for Stable Lithium Metal Anode.

ABSTRACT

Using 3D host is an effective way to solve the dendrite growth problem and accommodate volume changes of lithium (Li) metal anode. However, the preferred Li deposition on the top surface leads to the Li metal agglomeration at the surface. In addition, the large weight of the 3D host also greatly decreases the capacity based on the whole anode. Herein, a bidirectional lithiophilic gradient modification, including a top-down ZnO gradient and a bottom-up Sn gradient, is applied to an ultralight 3D carbon nanofiber host (density 0.1 g cm-3 ) and ensures the evenly filling lithium deposition in the 3D host. ZnO transforms into highly ionic conductive Li-Zn alloy and Li2 O during cycling, enhancing the Li-ion transportation from top to bottom. The metallic Sn also lowers the Li nucleation potential, guiding the preferential Li deposition from the bottom. With such a host, a stable CE of 97.5% over 100 cycles at 1 mA cm-2 and 3 mAh cm-2 is achieved, and the full battery also delivers good cycling stability over 300 cycles with a high CE of 99.8% coupled with high loading LiFePO4 cathode (10 mg cm-2 ) and low N/P ratio (≈3).