Surface Grafting SiO2 on Lithium-Rich Layered Oxide Cathode Material for Improving Structural Stability

Abstract

Surface grafting of SiO2 layer was carried out to alleviate the intrinsic issues of lithium-rich layered oxide Li1.2Mn0.54Ni0.13Co0.13O2 (LRLC). After analyzing the pristine and SiO2 coated samples by XRD, XPS, SEM and TEM characterizations, it is found that the surface of LRLC cathode material is successfully decorated with SiO2 layer while maintaining the pristine structure and morphology. The introduction of SiO2 coating prevents the erosion of cathode material from the electrolyte and inhibits the formation of spinel structure. More importantly, the capacity retention of the optimized 0.25 wt.% SiO2-coated LRLC sample after 200 cycles at 1 C delivers as high as 89.7%, much higher than that of the pristine sample (74.2%). There are obvious cracks on the surface of pristine sample after 200 cycles, while the surface of SiO2-coated LRLC samples remains intact, which convincingly proves that SiO2 layer can substantially promote the structural stability of cathode material. As last, the modification mechanism of SiO2 layer in the layered cathode material is elucidated. All in all, the shielding and scavenging effects of SiO2 protective layer towards HF hinder the electrolyte from corroding the cathode material, and improve the electrochemical performances, especially structure stability of the cathode material.