Comparison of fluorine sources on the electrochemical property of Li1.2Ni0.2Mn0.6O2 cathode materials

Abstract

Li-rich nickel manganese oxide materials are promising cathode materials for their high theoretical capacity and cobalt-free property. However, the poor cycle and rate performance still hamper their commercial application. In this study, fluorine-doped Li1.2Ni0.2Mn0.6O2 (LNMO) materials have been prepared successfully with different fluorine sources. XRD results verified that the (003) and (104) peaks of F-doped samples slightly shift to the lower diffraction angle than bare LNMO, and the large lithium slab distance of F-doped samples is beneficial for the transport and diffusion of Li+. The sample with PVDF as fluorine sources exhibits the best electrochemical performance than other F-doped LNMO samples. Specifically, this sample exhibits a high discharge capacity of 213.5[Formula: see text]mAh g−1 at 0.2 C (2.0–4.8 V), corresponding to a capacity retention of 88.7% after 100 cycles. The excellent electrochemical performance is due to the substitution of fluorine for oxygen sites with the host lattice, which can significantly enhance the Li+ migration and stabilize the layer structure of LNMO during the cycle process. These results demonstrated that PVDF was the best fluorine source to facilitate the electrochemical property of LNMO.