A Low Temperature Self-Assembled ZrO₂ Layer as a Surface Modification for High Energy Density Ni-Rich Cathode Materials in a Lithium-Ion Battery

Ni-rich layered oxide cathodes are an immediately applicable alternative for meeting the high energy density demand of lithium-ion batteries. The most significant hurdle of Ni-rich layered cathode materials is their poor cyclability because of their increasing surface resistance due to their electrochemically reactive surfaces causing side reactions and the occurrence of Li/Ni cation mixing. Surface coating has been extensively studied for safeguarding particles, thereby leading to increases in electrochemical performance; however, the synthesis conditions must be carefully controlled due to the fragile surface of a Ni-rich layered cathode. Herein, an effective coating method with self-assembled ZrO₂ (SA–ZrO₂) on the surface of a Ni-rich layered cathode material, LiNi_0.82Co_0.09Mn_0.09O₂ (NCM82), through a low-temperature self-combustion reaction is proposed. SA–ZrO₂ is built by a combustion reaction of Zr(SO₄)₂·4H₂O and thioacetamide to improve the surface stability of the cathode. In addition, a very small content of SO_x is retained from the precursor, which promotes high lithium diffusion on the surface. Systematic analyses by X-ray photoelectron spectroscopy and transmission electron microscopy demonstrate that this highly homogeneous ZrO₂ coating layer, which is prepared at a low temperature of 500 °C, largely enhances the electrochemical performance in the half-cell and full-cell.