On the functionality of the polypyrrole nanostructures for surface modification of Co-free Li-rich layered oxide cathode applied in lithium-ion batteries

Abstract

Co-free Li-rich manganese nickel oxide (LMNO) materials are emerging as an up-and-coming candidate for high-energy–density cathodes. However, they suffer from severe cycling capacity fading and poor performance rates. Herein, the surface functionalization of an LMNO cathode is designed by polypyrrole (PPy) nanostructure coating. We found that PPy [email protected] cathode exhibits high-capacity retention and enhanced rate capabilities, delivering a discharge capacity as high as 191 mAh g−1, with capacity retention of 96%, after ∼ 200 cycles at a current density of 20 mA g−1. The results indicate that the intercalation and doping pseudocapacitance can be varied depending on the synthesis process, morphology (nanowire/nanorod/nanoparticle), size, dispersity, and weight percentage of PPy. Our findings provide an effective strategy to improve the ionic and electronic conductivity of LMNO cathodes and demonstrate that high-capacity and long cycle-life Li-ion batteries can be achieved by regulating the contribution of the intercalation and doping pseudocapacitive charge storage behavior.