Investigation of the reversible lithiation of an oxide free aluminum anode by a LiBH4 solid state electrolyte

Abstract

In this study, we analyze and compare the physical and electrochemical properties of an all solid-state cell utilizing LiBH4 as the electrolyte and aluminum as the active anode material. The system was characterized by galvanostatic lithiation/delithiation, cyclic voltammetry (CV), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), Raman spectroscopy, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM). Constant current cycling demonstrated that the aluminum anode can be reversibly lithiated over multiple cycles utilizing a solid-state electrolyte. An initial capacity of 895 mAh/g was observed and is close to the theoretical capacity of aluminum. Cyclic voltammetry of the cell was consistent with the constant current cycling data and showed that the reversible lithiation/delithiation of aluminum occurs at 0.32 V and 0.38 V (vs. Li+/Li) respectively. XRD of the aluminum anode in the initial and lithiated state clearly showed the formation of a LiAl (1:1) alloy. SEM-EDS was utilized to examine the morphological changes that occur within the electrode during cycling. This work is the first example of reversible lithiation of aluminum in a solid-state cell and further emphasizes the robust nature of the LiBH4 electrolyte. This demonstrates the possibility of utilizing other high capacity anode materials with a LiBH4 based solid electrolyte in all-solid-state batteries.