Investigation on graphitic carbon foams - LiNiyPO4 (y=0.8-1.0) composites

Graphitic carbon foams coated with olivine-structured lithium nickel phosphate (LiNiyPO4) (y = 0.8-1.0) as possible cathode materials for 5 V applications are investigated. The composites are prepared by soaking the foams into solutions containing lithium, nickel ions and phosphates, treated in flowing air then in flowing nitrogen. The structural, morphological and electrochemical properties are strongly dependent upon the Ni-content. The X-ray diffractograms, performed on powders prepared under very similar conditions, showed the formation of LiNiPO4 phase with Li4P2O7 and Li2Ni3(P2O7)(2). The morphological investigation revealed a dramatic change of the layer by decreasing the Ni-content. The voltammetric curves show values of the mean peak maxima in the anodic region between 5.1 and 5.2 V and in the cathodic region between 4.88 for (y = 1.0) and similar to 5.18 V for (y = 0.9 and 0.8) respectively. The specific capacity of the composites (at the first cycle, a discharge rate of C/10 and room temperature) increases by decreasing the nickel content into the cathode material reaching a maximum of 122 mAh g(-1) for y = 0.8. (C) 2012 Elsevier Masson SAS. All rights reserved.