Bifunctional 3D Graphite@Ni-Fe foam negative current collector toward stable liquid metal battery

Abstract

Negative current collectors play vital roles in the electrochemical performance of liquid metal batteries (LMBs). Employing a three-dimensional (3D) current collector is an effective approach to host molten lithium and reduce the effective current density. The Ni-Fe foam is a frequently used 3D current collector for the negative electrode. However, the corrosion of molten lithium towards the Ni-Fe foam skeleton devastates the 3D structure of the current collector and so deteriorates seriously the electrochemical performance of LMB. To enhance the corrosion resistivity, herein, the graphite layer coated Ni-Fe foam (Graphite@Ni-Fe) is prepared by the chemical vapor deposition method. The prepared scaly-like graphite layer plays a bifunctional role in chemistry, preventing corrosion as an effective barrier and improving remarkably the surface lithiophilicity of Ni-Fe foam. The assembled Li||Bi batteries with Graphite@Ni-Fe foam as negative current collector exhibit stable cycling performance with capacity retention of 98.10% and high Coulombic efficiencies over 98.3% at 0.4 A cm−2 over 100 cycles at 500 °C. More importantly, outstanding rate capability is achieved and almost no capacity degradation is observed upon current density change from 0.2 to 2.0 A cm−2. This work highlights the importance of the lithiophilicity and the corrosion resistance ability of the negative current collectors for LMBs.