Enhanced electrochemical performance of LiNi0.8Co0.1Mn0.1O2 cathode materials via Li4P2O7 surface modification for Li-ion batteries

The performance of LiNi0.8Co0.1Mn0.1O2 cathode materials has been significantly improved by Li4P2O7 surface modification. Some electrochemical tests are carried out to investigate the relevant performances of LiH2PO4 coated LiNi0.8Co0.1Mn0.1O2 , such as inductively coupled plasma test (ICP), scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The results indicate that LiNi0.8Co0.1Mn0.1O2 is clad with a layer of average thickness about 30-40 nm. And the alkalinity on the surface of the modified materials has declined dramatically after titration measurement. The effect of surface modification can be credited to the two main factors: On the one hand, the weak acidity of LiH2PO4 neutralizes the lithium residues (LiOH/Li2CO3) on the surface of LiNi0.8Co0.1Mn0.1O2 cathode materials; on the other hand, LiH2PO4 continues to decompose and react with the unneutralized lithium residues to generate a coating layer of Li4P2O7 during the annealing process, which can prevent the active materials from contacting with the electrolyte directly and act as an outstanding Li+ conductor, thus inhibiting the interface reaction and improving the cycle performance as well as the rate properties of the host materials.