Hight voltage lithium cobalt phosphate with nitrogen doped carbon coating layer for ultrahigh performance lithium ion battery

Abstract

In this study, we successfully synthesized a novel LiCoPO4 (LCP) nanosheet cathode materials with nitrogen and fluorine co-doped carbon layer (LCP/C–NF) using a solvothermal method and carbonization process in multiple carbon sources including sucrose, polyvinylidene fluoride (PVDF), and cetyltrimethylammonium bromide (CTAB). The LCP nanosheets possess a high exposure of (010) crystal planes which shortens the Li+ transport path. The N and F co-doped carbon coating layer had more defects and facilitates the formation of Co–N and Co–F bonds at the interface between the carbon coating and LCP, resulting in improved interface stability and suppressed Co element dissolution. LCP/C–NF exhibits excellent discharge capacity of 126.69 mAh g−1 at a current rate of 1 C, with a capacity retention of 98.99% after 200 cycles and 64.94% after 1000 cycles. At a high current density of 10 C, the initial specific capacity is 112.1 mAh g−1, with a capacity retention of 53.32% after 500 cycles. Additionally, this material maintains high electrochemical activity even at low temperatures of 0 and -15 °C. The N and F co-doped carbon coating method has a strategic significance in the industrial application of high voltage Olivine-type lithium cobalt phosphate cathode materials.