“…After 200 cycles, the discharge capacities of the samples NCM, PPy1, PPy3, PPy5 and PPy7 are 76, 74, 105, 128 and 98 mA h g −1 , corresponding to a capacity retention ratio of 41.1%, 38.5%, 55.5%, 67.2% and 56.3%, respectively. Previous reports have shown that highly acid HF generated from the decomposition of the electrolyte during charge‐discharge process can erode the surface of cathode materials to destroy the surface structure of electrode, resulting in a poor cycling performance . In present investigation, PPy as a protective layer coated on the surface of cathode can effectively prevents the surface from the direct exposing to the electrolyte and corroding by HF.…”