Exploration of Alnico alloy as a magnetic electrode material for lithium-ion batteries

Abstract

The search for a reliable indicator of state-of-charge and even the remaining energy of a lithium-ion cell is of great importance for various applications. This study was an exploratory effort to use magnetic susceptibility as the indicator. Magnetic Alnico alloy was investigated as an anode material for rechargeable lithium batteries. Both pristine and partially oxidized Alnico powders were made into electrodes. Structural characterization was performed on the Alnico electrodes by means of X-ray diffraction, scanning electron microscopy, and inductively coupled plasma analysis. The electrochemical cycling of cells made of the Alnico electrodes against lithium was measured. The first lithium intercalation capacity of a treated Alnico can be up to about 600 mAh/g, while a rather reversible capacity of up to 180 mAh/g can be obtained. The capacity increases with the extent of oxidation of Alnico. It was observed that the ac susceptibility of an electrode changes with depth-of-discharge (DOD). We have proposed an electrode model with a core-shell structure, which can explain this susceptibility vs. DOD relationship.