Surface modification of Li1.2Mn0.54Co0.13Ni0.13O2 with conducting polypyrrole

The lithium-rich solid solutions between layer-structured Li2MO3 (M = Mn, Zr, Ti) and LiM′O2 (M′ = Mn0.5Ni0.5, Mn0.33Co0.33Ni0.33, Co, etc.) are attractive cathode materials for lithium ion batteries with high specific energies. However, these solid solutions suffer from low coulombic efficiency due to the loss of oxygen in the form of Li2O and electrolyte decomposition at high potentials in the initial cycle and poor cyclability due to decreased number of sites for lithium ion insertion/extraction in the subsequent cycles. In addition, the presence of a solid electrolyte interphase layer on these solid solutions is still in argument. In this work, Li1.2Mn0.54Co0.13Ni0.13O2 (0.5Li2MnO3·0.5LiMn0.33Co0.33Ni0.33O2) is prepared by Pechini method and coated with conducting polypyrrole (PPy). The physical characterization (XRD, SEM, HRTEM, FTIR) and electrochemical evaluation (EIS, CV and galvanostatic cycling) demonstrate the effectiveness of the surface modification on improving the electrochemical performances of the solid solution and the presence of a solid electrolyte interphase layer on the charged PPy-modified material.

► Li1.2Mn0.54Co0.13Ni0.13O2 (LMO) is surface-coated with conducting polypyrrole (PPy).
► Coating improves the initial coulombic efficiency and capacity retention of LMO.
► SEI layer is observed and its composition recognized on PPy-coated LMO at 4.8 V.