Poly(vinyl chloride) (PVC) coated idea revisited: Influence of carbonization procedures on PVC-coated natural graphite as anode materials for lithium ion batteries

The influence of carbonization procedures on poly(vinyl chloride) (PVC) coated natural graphite (NG) spheres as anode materials for lithium ion batteries was investigated in detail in this study. At first, thermogravimetry-mass spectrometry was utilized to analyze pyrolysis behaviors of PVC, and on the basis of the results three typical carbonization procedures consisting of different heating steps were determined to fabricate PVC-coated NG spheres. The structural parameters, morphologies, pore size distributions, and Brunauer-Emmett-Teller specific surface areas of these coated samples were systematically characterized by employing X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and N-2 adsorption/desorption isotherms. Electrochemical performance measurements indicated that all the coated samples display a significantly improved cyclability, rate capability, and initial Coulombic efficiency in comparison with the pristine NG spheres. The reasons for the performance improvement were further explored using electrochemical impedance spectroscopy. Moreover, the sample under the carbonization procedure involving isothermal heating steps at temperatures of 280, 450, and 900 degrees C is even better than the well-recognized mesocarbon microbeads in terms of reversible capacity and rate capability.