No abstract

The crystal orientation of LiFePO4 was controlled by using a magnetic field to facilitate favorable transport kinetics for lithium ions.

The crystal alignment technology of lithium nickel manganese oxide (LiNi0.5Mn0.3Co0.2O2) is proposed using its magnetic properties. The crystalline LiNi0.5Mn0.3Co0.2O2 exhibits the paramagnetic behavior at room temperature as well as the magnetic anisotropy originated from its crystallographic anisotropy. If the crystalline LiNi0.5Mn0.3Co0.2O2 is exposed to a magnetic field, it can tend to rotate to an angle minimizing its system energy due to spontaneous magnetization. Taking these magnetic natures into account, the vector quantity of an external magnetic field (i.e., magnetic flux density and field direction) is adjusted to apply to a viscous LiNi0.5Mn0.3Co0.2O2 slurry coated onto a current collector; thus, the crystal aligned LiNi0.5Mn0.3Co0.2O2 electrode is obtained, in which the (00 l) plane is notably oriented perpendicular to the surface of a current collector. The aligned LiNi0.5Mn0.3Co0.2O2 electrode consistently records superior electrochemical performance to a pristine LiNi0.5Mn0.3Co0.2O2 electrode because the former demonstrates an improved capability of lithium ion transport during the charge/discharge process in a lithium ion battery. The aligned LiNi0.5Mn0.3Co0.2O2 is considered to have the improved transport capability because the kinetics of lithium ion transport in LiNi x Mn y Co1-(x+y)O2 intrinsically occurs along the (00 l) plane.

We studied technology that enables the crystal alignment of LiNi0.5Mn0.3Co0.2O2 using its magnetic properties. LiNi0.5Mn0.3Co0.2O2 exhibited either antiferromagnetic or paramagnetic behavior depending on temperature as well as magnetic anisotropy originated from its crystallographic anisotropy. Based on these magnetic characteristics, we adjusted the vector quantity of an external magnetic field and applied it to LiNi0.5Mn0.3Co0.2O2 crystals, thus producing crystal-aligned LiNi0.5Mn0.3Co0.2O2 electrodes. In these electrodes, the (00l) plane was oriented comparatively perpendicular to the surface of a current collector. Due to the intrinsic lithium ion transport kinetics in LiNi0.5Mn0.3Co0.2O2 along the (00l) plane, aligned LiNi0.5Mn0.3Co0.2O2 may contribute to enhancing lithium ion conduction during the charge/discharge process in a lithium ion battery, resulting in improved electrochemical performance.