Surface Grafting SiO 2 on Lithium-Rich Layered Oxide Cathode Material for Improving Structural Stability

Surface grafting of SiO 2 layer was carried out to alleviate the intrinsic issues of lithium-rich layered oxide Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 (LRLC). After analyzing the pristine and SiO 2 coated samples by XRD, XPS, SEM and TEM characterizations, it is found that the surface of LRLC cathode material is successfully decorated with SiO 2 layer while maintaining the pristine structure and morphology. The introduction of SiO 2 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.% SiO 2 -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 SiO 2 -coated LRLC samples remains intact, which convincingly proves that SiO 2 layer can substantially promote the structural stability of cathode material. As last, the modification mechanism of SiO 2 layer in the layered cathode material is elucidated. All in all, the shielding and scavenging effects of SiO 2 protective layer towards HF hinder the electrolyte from corroding the cathode material, and improve the electrochemical performances, especially structure stability of the cathode material.