High nitrogen content carbons: morphological and chemical changes with synthesis temperature and application in Lithium-Sulfur batteries

ARIAS, ANALIA NATALI; VILLARROEL-ROCHA, JHONNY; SAPAG, KARIM; MORI, MARÍA FERNANDA; PLANES, GABRIEL ANGEL; TESIO, ALVARO YAMIL; FLEXER, VICTORIA

ELECTROCHIMICA ACTA

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2020

0013-4686

We present a new two-step synthesis method to prepare nitrogen-doped carbons with micro, meso and macroporosity. We modified the classical polycondensation of resorcinol?formaldehyde, by adding a large excess of melamine in basic medium. A series of materials were prepared by varying the maximum carbonization temperature in the range 600 ? 900 °C, and are denoted NCC-X, where X denotes that maximum temperature. NCC-X showed a high nitrogen content, ranging from 32.9 % to 10.3 %. Scanning electron microscopy showed macropores in the order of 100 -600 nm, with sizes decreasing with temperature, reaching a minimum for NCC-800, and then increasing again. N2 adsorption-desorption isotherms showed the presence of micro and mesopores for all samples, with a maximum surface area of 505 m2 g−1 for NCC-800. CO2 adsorption isotherms showed that all NCC-X materials present ultramicropores. NCC-X were incorporated as host materials for elemental sulfur in lithium-sulfur batteries. The increased narrow micropore volume of materials pyrolysed at higher temperature seems to promote an initial higher cell capacity. Conversely, the much higher N content and the higher amount of N in pyridinic environments were identified as the reasons for the higher cycling stability of the cells prepared with NCC-600 and NCC-750.