Crystal alignment of a LiFePO₄ cathode material for lithium ion batteries using its magnetic properties

Abstract

We suggest a way to control the crystal orientation of LiFePO₄ using a magnetic field to obtain an advantageous structure for lithium ion conduction. We examined the magnetic properties of LiFePO₄ such as magnetism and magnetic susceptibility, which are closely related to the crystal rotation in an external magnetic field, and considered how to use these properties for desired crystal orientation; thus, we successfully fabricated the crystal-aligned LiFePO₄, in which the <i>b</i>-axis was highly aligned perpendicular to the surface of a current collector. Considering the low lithium ion conductivity of LiFePO₄ inherently originated from its one-dimensional path for lithium ion diffusion, the crystal-aligned LiFePO₄ potentially facilitates favorable transport kinetics for lithium ions during the charge/discharge process in lithium ion batteries. The crystal-aligned LiFePO₄ should afford lower electrode polarization than pristine LiFePO₄, and thus the former consistently exhibited higher reversible capacity than the latter.