Effect of the Mg-substitution on the graphitic carbon foams—LiNi1−yMgyPO4 composites as possible cathodes materials for 5 V applications

The characterization of composites consisting of graphitic carbon foams coated with olivine structured LiNi1−yMgyPO4 (0 ≤ y ≤ 0.3) prepared by a Pechini assisted sol–gel process, is reported. The structural, morphological and electrochemical properties were found to be dependent upon the Mg-content. After annealing in nitrogen at T = 785 °C, the formation of the LiNiPO4 phase on the graphitic foams is observed. The morphological investigation reveals a layer on the graphitic foams that consists of irregular shaped particles. The size of the particles remains constant by increasing the magnesium content. The voltammetric curves show values of the reduction/oxidation mean peaks in the range of ∼5.0 V and 5.2–5.3 V respectively. The specific capacity of the composites (at the first cycle, a discharge rate of C/10 and room temperature) increases by substituting Mg-ions for Ni-ions, and reaches 126 mAh g−1 (at a discharge rate of C/10 and room temperature) for y = 0.2.

Graphical abstractThe substitution of more electropositive Mg-ions for Ni2+ ions in the graphitic carbon foam – LiNi1−yMgyPO4 composites increases dramatically the specific capacity of the composites up to 126 mAh g−1.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Commercial graphitic carbon foams coated with LiNi1−yMgyPO4 as cathode materials. ► Investigation of the effect of Mg2+ substitution for Ni2+ ions. ► Specific capacity of 126 mAh g−1 at 0.1 C and RT for y = 0.2.