Modification of Carbon Anode of Lithium Ion Secondary Battery

Carbonaceous materials based upon melamine resin and doped with phosphorous were obtained by heat-treatment and were analyzed by elemental analysis, XPS and XRD. The results showed that the addition of phosphoric acid did not affect severely the content of nitrogen, but greatly affected the relative content of graphene nitrogen. The addition favors the increase of reversible lithium capacity. The addition of phosphoric acid resulted in a decrease of carbonization degree at lower temperature (600°C) and no much changes at higher temperature (800°C). The phosphorous added was dispersed homogeneously in the carbon materials and bonded not only with oxygen atom but also with the carbon structure, and the later bond was strengthened at higher temperature. All these factors lead to the changes of reversible capacity. At lower temperature, the reversible capacity below 0.9 V decreased with the amount of added phosphoric acid, while at higher temperature, the reversible capacity above 0.9 V increased. The reversible capacity of the carbon obtained in this work can reach 516 mA·h·g^-1.