The kinetic and thermodynamic analysis of Li+ in multi-walled carbon nanotubes

The multi-walled carbon nanotubes (MWNTs) prepared by CVD were used in electrochemical intercalation reaction with Li+. The results of the first several charge-discharge cycles showed that the reversible capacity of the MWNTs was larger than the theoretical capacity of graphitized carbon. The equivalent circuit of the Li+ intercalated into the MWNTs was simulated The diffusion coefficient calculated based on the results of the impedance was in the range between 1 similar to 4x 10(-10) cm(2)s(-1). The diffusion coefficient calculated based on the technique of the chronoamperometery was 3.5 x 10(-10) cm(2)s(-1). The diffusion coefficients of the Li+ reacted with MWNTs was in the range of that of the most carbon materials. Using EMF method the partial molar entropy (Delta S-x) and partial molar enthalpy (Delta H-x) of the Li+ intercalated into the MWNTs were calculated as a function of x in LixC6 at different temperatures. The values of Delta S-x were in the range of 150 similar to 550 J mol(-1)K(-1). The values of Delta H-x at 35 degrees C were ill the range of 40 similar to 110 kJ mol(-1). Both of the Delta S-x and Delta H-x were lower and the changes were smaller than the values of some other carbonaceous materials. By analyzing the results conclusion is obtained that Li+ exist in MWNTs with different types which include adsorption and intercalation types.