Improvement of the high-rate capability of LiNi1/3Co1/3Mn1/3O2 cathode by adding highly electroconductive and mesoporous graphene

The electrochemical properties of NCM cathodes with various conductive additives have been comparatively studied in this work. The conductive additives are porous graphene/carbon black (SG), carbon black/conductive graphite (SK), carbon black (SC), and conductive graphite (KS), respectively. The results suggest that the NCM electrode with SG conductive additive shows the best rate performance, which exhibits a discharge capacity of 78 mAh g−1 at the current density of 2000 mA g−1 in the voltage range of 2.5-4.1 V versus lithium electrode, that is ∼1.7 times higher than that of NCM electrode with SK additive. The electrochemical impedance spectra (EIS) results reveal that the NCM electrode with SG addition has the lowest charge transfer resistance. On this basis, the structural evolution of NCM material with SG conductive additive in the first charge process has been studied via an in situ synchrotron X-ray diffraction technique (XRD). The XRD patterns show that a thorough phase transition from hexagonal H1 to hexagonal H2 occurs at the voltage of 4.3 V, and the diffraction peaks of (0 1 8)/(1 1 0) splits gradually, representing the extraction of lithium from the ordered layer-structured NCM materials.